Air compression apparatus and method of use

ABSTRACT

An air compression apparatus has a frame, a tank, and a motor. A drive mechanism is operably connected to the motor and at least one piston assembly is operably connected to the drive mechanism and configured to move within a respective cylinder mounted to the frame. The piston assembly includes: (1) a piston body; (2) a piston rod having a hollow bore connected at one end to the drive mechanism and at an opposite end to the piston body; and (3) a piston valve installed on the piston body. In use, upward travel of the piston body as caused by the drive mechanism acting through the piston rod opens the piston valve and allows ambient air to be drawn through the hollow bore into the cylinder, and downward travel of the piston body closes the piston valve so as to compress the air within the cylinder.

RELATED APPLICATIONS

This application claims priority to and is entitled to the filing dateof U.S. Provisional application Ser. No. 60/573,250 filed May 21, 2004,and entitled “Multi-Stage Compressor with Integrated InternalBreathing,” and U.S. Provisional application Ser. No. 60/652,694 filedFeb. 14, 2005, and entitled “Compressor with Variable-Speed PressureStroke.” The contents of the aforementioned applications areincorporated herein by reference.

INCORPORATION BY REFERENCE

Applicant hereby incorporates herein by reference any and all U.S.patents and U.S. patent applications cited or referred to in thisapplication.

TECHNICAL FIELD

Aspects of this invention relate generally to air compression systems,and more particularly to an apparatus and method for compressing airintroduced into a cylinder through a hollow piston rod.

BACKGROUND ART

The following art defines the present state of this field:

Great Britain Patent No. GB 1043195 to Grant describes a reciprocatingpiston compressor or air motor having a plurality e.g. four cylindersextending radially from an axial valve chamber housing four angularlyspaced ports and in which is rotatably mounted an axially adjustabletubular cylindrical distributing valve provided in a central portionwith a suction port and a delivery port and adapted to be brought intosequential communication with each valve chamber port, the outer surfaceof the valve body is provided with a groove which at or immediatelyprior to opening of delivery port serves to connect the valve chamberport to an annular chamber bounded in part by the drive end of the valvebody and the pressure therein acts against the discharge pressure in anannular chamber at the other end of said valve body and the resultingaxial displacement of the valve controls the time of opening of thevalve ports according to whether the pressure in one chamber is below orabove that in another chamber. The valve portion comprises concentrictubes connected by webs and through which the suction port extendswhilst the delivery port extends through the outer tube only. An axialextension tube provides air inlet means to said suction port. Each ofthe four valve chamber ports are roughly triangular and have a sideparallel to the valve axis, a side normal to the axis and the third sidehas two portions of differing slopes which register with portions of theleading edge of the inlet port and with the leading edge of the deliveryport. Lubricant is admitted to a bore leading to grooves and coolingwater admitted through a pipe traverses a jacket surrounding the valveand a space round each cylinder. The pistons are each secured to across-head connected together in diametrically opposed pairs by theoutside member whilst adjacent pistons are connected by connectingmembers and the cross-heads are reciprocated by two eccentric rings eachrotatable within a slide block and having secured thereto a dished disc.The latter are secured together at their peripheries by bars and havebalancing weights.

Great Britain Patent No. GB 1259755 to Sulzer Brothers Ltd. describes acompressor wherein a piston reciprocates in a cylinder without normallymaking physical contact with the cylinder, the piston being providedwith a split ring having longitudinal grooves in its periphery. The ringmay be of P.T.F.E. and acts to guide the piston in the event of abnormaloperation causing the piston to approach the cylinder. During normaloperation gas escaping past labyrinth seals or labyrinths formed in theperiphery of the piston, acts on a conical ring to centre the piston.Radial holes pass through the ring and open into the grooves thereby toprovide pressure equalization between the inside and outside of thering. The piston may be double or, as shown, single acting and driven bya piston rod which extends through a cylinder seal for connection to across-head.

U.S. Pat. No. 4,373,876 to Nemoto describes a compressor having a pairof parallel, double-headed pistons reciprocally mounted in respectivecylinder chambers in a compressor housing. The pistons are mounted on acrankshaft via Scotch-yoke-type sliders slidably engaged in therespective pistons for reciprocating movement in a direction normal tothe piston axis. The sliders convert the rotation of the crankshaft intolinear reciprocation of the pistons. The dimensions of these sliders aredetermined in relation to the other parts of the compressor so that,during the assemblage of the compressor, the sliders may be mounted inposition by being passed over the opposite end portions of thecrankshaft following the mounting of the pistons and crankshaft withinthe housing.

U.S. Pat. No. 5,050,892 to Kawai, et al. describes a piston for acompressor comprising a ring groove on the outer circumferential surfaceof the piston, and a discontinuous ring seal member with opposite splitends made of a plastic material and fitted in the ring groove. The ringmember having an outer surface comprising a main sealing portion havingan axially uniform shape and an outwardly circumferentially projectingflexible lip portion. Also, the inner surface of the ring membercomprises an inner bearing portion able to come into contact with afirst portion of a bottom surface of the ring groove such that theflexible lip portion of the outer surface is brought into contact with acylinder wall of the cylinder bore and preflexed inwardly. An innerpressure receiving portion is formed adjacent to the inner bearingportion to receive pressure from the compression chamber, to furtherflex the flexible lip portion upon a compression stroke of thecompressor and thereby allow the ring member to expand and the mainsealing portion to come into contact with the cylinder wall of thecylinder bore.

Japanese Patent Application Publication No. JP 1985/0079585 to Michio,et al. describes a displacer rod bearing body, provided at its upper andlower parts with rod pin mounting parts, and reciprocatively slides adisplacer rod bearing surface around a cross rod pin of a cross head. Adisplacer rod, secured to a displacer, is rotatably supported to anupper rod pin of the bearing body, and a compressor for the displacer isrotatably supported to a lower rod pin.

U.S. Pat. No. 5,467,687 to Habegger describes a piston compressor havingat least one cylinder and a piston guided therein in a contact-freemanner, which is connected via a piston rod to a crosshead. The pistonrod consists of a pipe extending between the crosshead and the piston.In this pipe extends a tension rod, which can be extended by means of ahydraulic stretching device and under prestressing pulls the crossheadand the piston towards the pipe.

U.S. Pat. No. 6,132,181 to McCabe describes a windmill having aplurality of radially extending blades, each being an aerodynamic-shapedairfoil having a cross-section which is essentially an invertedpan-shape with an intermediate section, a leading edge into the wind,and a trailing edge which has a flange doubled back toward the leadingedge and an end cap. The blade is of substantial uniform thickness. Anair compressor and generator are driven by the windmill. The compressoris connected to a storage tank which is connected to the intake of asecond compressor.

U.S. Patent Application Publication No. US 2002/0061251 to McCabedescribes a windmill compressor apparatus having multiple double actingpiston/cylinders actuated by the windmill. The windmill additionally hasmultiple pairs of blades to enhance power output and lift.

U.S. Pat. No. 6,655,935 to Bennitt, et al. describes a gas compressorand method according to which a plurality of inlet valve assemblies areangularly spaced around a bore. A piston reciprocates in the bore todraw the fluid from the valve assemblies during movement of the pistonunit in one direction and compress the fluid during movement of thepiston unit in the other direction and the valve assemblies preventfluid flow from the bore to the valve assemblies during the movement ofthe piston in the other direction. A discharge valve is associated withthe piston to permit the discharge of the compressed fluid from thebore.

U.S. Pat. No. 6,776,589 to Tomell et al. describes a reciprocatingpiston compressor having a suction muffler and a pair of dischargemufflers to attenuate noise created by the primary pumping frequency inthe primary pumping pulse. The suction muffler is disposed along asuction tube extending between the motor cap and the cylinder head ofthe compressor. The discharge mufflers are positioned in series withinthe compressor to receive discharge gases from the compression mechanismand are spaced one quarter of a wavelength from each other so as tosequentially diminish the problematic or noisy frequencies createdduring compressor operation. The motor/compressor assembly including themotor and compression mechanism is mounted to the interior surface ofthe compressor housing by spring mounts. These mounted are secured tothe housing to define the position of the nodes and anti-nodes of thefrequency created in the housing to reduce noise produced by naturalfrequencies during compressor operation.

The prior art described above teaches single and double-acting aircylinders, but does not teach introducing air into an air cylinderthrough a hollow piston rod and applying varied speed and pressure tothe piston body attached to the piston rod corresponding to thecompressive work being done by the piston during its stroke. Aspects ofthe present invention fulfill this need and provide further relatedadvantages as described in the following disclosure.

DISCLOSURE OF INVENTION

Aspects of the present invention teach certain benefits in constructionand use which give rise to the exemplary advantages described below.

An air compression apparatus has a frame and a tank and a motor mountedto the frame. A drive mechanism is operably connected to the motor andat least one piston assembly is operably connected to the drivemechanism and configured to move within a respective cylinder mounted tothe frame. The piston assembly includes: (1) a piston body sealingly andslidably installed within the cylinder so as to form an upper chamberabove the piston body and a lower chamber below the piston body, thepiston body being further formed with a cavity in communication with atleast the lower chamber; (2) a piston rod having a hollow borecommunicating between a drive end and a piston end, the drive end beingconnected to the drive mechanism such that the hollow bore is incommunication with ambient air, the piston rod passing through thecylinder and the upper chamber so as to be connected at the oppositepiston end to the piston body, the piston rod having at least oneopening formed therein substantially at the piston end such that thehollow bore is in communication with the cavity; and (3) a lower pistonvalve installed on the piston body so as to selectively seal the lowerchamber from the cavity. In use, upward travel of the piston body ascaused by the drive mechanism acting through the piston rod opens thelower piston valve and allows ambient air to be drawn through the hollowbore, the at least one opening, and the cavity into the lower chamber,and downward travel of the piston body as caused by the drive mechanismacting through the piston rod closes the lower piston valve so as tocompress the air within the lower chamber.

An aspect of the present invention may then be generally described as animproved air compression system where ambient air is introduced into acylinder through a hollow piston rod so as to improve the air flowthrough the cylinder, resulting in more efficient and quiet operation.

A further aspect of the present invention may be generally described assingle-acting or double-acting air compression cylinders each configuredwith a piston body having a cavity that is selectively sealed by one ormore valves opening to allow the passage of ambient air through thehollow piston rod into a chamber within the cylinder above or below thepiston body and alternately closing to compress the air within suchchamber, further improving the efficiency of the air compression system.

A still further aspect of the present invention may be generallydescribed as a drive mechanism for oscillating the piston body withineach cylinder such that relatively greater force is applied to thepiston body through the piston rod during peak air compression whilerelatively less force is applied to the piston body through the pistonrod during most of the air gathering through the hollow piston rod,resulting is further improvements in operation of the air compressionsystem.

Other features and advantages of aspects of the present invention willbecome apparent from the following more detailed description, taken inconjunction with the accompanying drawings, which illustrate, by way ofexample, the principles of aspects of the invention.

BRIEF DESCRIPTION OF DRAWINGS

The accompanying drawings illustrate aspects of the present invention.In such drawings:

FIG. 1 is a perspective view, partially in section, of an exemplaryembodiment of the air compression apparatus of the present invention;

FIG. 2 is an enlarged perspective view thereof taken from circle “2” ofFIG. 1;

FIG. 3 is a front view of an alternative exemplary embodiment of the aircompression apparatus of the present invention;

FIG. 4 is a reduced scale front view thereof in a first position ofoperation;

FIG. 5 is a reduced scale front view thereof in a second position ofoperation;

FIG. 6 is a reduced scale front view thereof in a third position ofoperation;

FIG. 7 is front view of an alternative exemplary embodiment of the aircompression apparatus of the present invention in a first position ofoperation;

FIG. 8 is a front view thereof in a second position of operation;

FIG. 9 is a front view thereof in a third position of operation;

FIG. 10 is a front view thereof in a fourth position of operation;

FIG. 11 is a front view thereof in a fifth position of operation;

FIG. 12 is a front view thereof in a sixth position of operation;

FIG. 13 is a front view of an alternative exemplary embodiment of theair compression apparatus of the present invention;

FIG. 14 is a front view of an alternative exemplary embodiment of theair compression apparatus of the present invention;

FIG. 15 is a front view of an alternative exemplary embodiment of theair compression apparatus of the present invention;

FIG. 16 is a front view, partially in section, of an alternativeexemplary embodiment of the air compression apparatus of the presentinvention;

FIG. 17 is a side view thereof;

FIG. 18 is a front view, partially in section, of an alternativeexemplary embodiment of the air compression apparatus of the presentinvention;

FIG. 19 is an enlarged scale sectional view taken from circle “19” ofFIG. 18;

FIG. 20 is a sectional view thereof in a first mode of operation;

FIG. 21 is a sectional view thereof in a second mode of operation;

FIG. 22 is a front view, partially in section, of an alternativeexemplary embodiment of the air compression apparatus of the presentinvention;

FIG. 23 is an enlarged scale sectional view taken from circle “23” ofFIG. 22;

FIG. 24 is a sectional view thereof in a first mode of operation;

FIG. 25 is a sectional view thereof in a second mode of operation;

FIG. 26 is a sectional view thereof in a third mode of operation;

FIG. 27 is a sectional view thereof in a fourth mode of operation;

FIG. 28 is partial sectional front view of an alternative exemplaryembodiment of the air compression apparatus of the present invention;

FIG. 29 is an top view thereof taken along line “29-29” of FIG. 28;

FIG. 30 is a reduced scale sectional view thereof in a first mode ofoperation;

FIG. 31 is a reduced scale sectional view thereof in a second mode ofoperation;

FIG. 32 is a partial sectional front view of an alternative exemplaryembodiment of the air compression apparatus of the present invention;

FIG. 33 is a reduced scale top view thereof taken along line “33-33” ofFIG. 32;

FIG. 34 is a reduced scale sectional view thereof in a first mode ofoperation;

FIG. 35 is a reduced scale sectional view thereof in a second mode ofoperation;

FIG. 36 is a partial sectional front view of an alternative exemplaryembodiment of the air compression apparatus of the present invention;

FIG. 37 is a reduced scale top view thereof taken along line “37-37” ofFIG. 36;

FIG. 38 is a partial sectional front view of an alternative exemplaryembodiment of the air compression apparatus of the present invention ina first mode of operation;

FIG. 39 is a reduced scale top view thereof taken along line “39-39” ofFIG. 38;

FIG. 40 is an enlarged scale partial sectional front view thereof in asecond mode of operation;

FIG. 41 is a partial sectional front view of an alternative exemplaryembodiment of the air compression apparatus of the present invention ina first mode of operation;

FIG. 42 is a reduced scale top view thereof taken along line “42-42” ofFIG. 41;

FIG. 43 is a partial sectional front view thereof in a second mode ofoperation;

FIG. 44 is a partial sectional front view of an alternative exemplaryembodiment of the air compression apparatus of the present invention ina first mode of operation;

FIG. 45 is a top view thereof taken along line “45-45” of FIG. 44;

FIG. 46 is a partial sectional front view thereof in a second mode ofoperation;

FIG. 47 is a partial perspective view of an alternative exemplaryembodiment of the air compression apparatus of the present invention;

FIG. 48 is a sectional view thereof taken along line “48-48” of FIG. 47;

FIG. 49 is a left side view of an alternative exemplary embodiment ofthe air compression apparatus of the present invention;

FIG. 50 is a front view thereof; and

FIG. 51 is a right side view thereof.

MODES FOR CARRYING OUT THE INVENTION

The above described drawing figures illustrate aspects of the inventionin at least one of its exemplary embodiments, which are further definedin detail in the following modes.

The subject of this patent application is an improved air compressionapparatus, where “air” as used throughout is to be understood to meanand apply to any compressible medium, whether gas or liquid. The aircompression apparatus described herein is an assembly made up in part ofone or more cylinders, each containing a piston which is driven by a rodconnected to a crank. The connection between the rod and the crankmechanism can take many forms depending on the design and application,but is typically achieved by attaching the free end of the rod to aflywheel, pivoting arm, or cam follower arrangement so that the cylindermoves relative to the crank in a manner that manipulates the velocity oftravel of the piston and thereby increases the leverage exerted againstthe compressed air when the piston is approaching its top and bottompositions, or highest points of compression. It will be appreciated bythose skilled in the art that while the general structure and operationof the improved air compressor of the present invention is shown anddescribed herein in various exemplary embodiments, the invention is notso limited. Rather, a key inventive aspect of the improved compressorthat transcends any particular design and construction is the principlethat a relatively longer or larger volume working stroke of each pistoncombined with a coordinated variance in the speed of the piston duringits stroke produces smoother and more efficient compression. Suchrelatively longer or larger volume stroke and/or speed variance of eachpiston is achieved in each of the exemplary embodiments of the presentinvention described hereinafter, the descriptions of which will furtherinform those skilled in the art of the novel principles of operation andstructure of the air compression apparatus and provide a context forgreater appreciation of its benefits. Specifically, embodiments areshown and described as having relatively smaller diameter, longer strokecylinder configurations for smooth air gathering and compression atrelatively lower speeds and as having relatively larger diameter,shorter stroke cylinder configurations that are able to operateefficiently at relatively higher speeds as compared to the longer strokecylinder configurations due to reduced inertial effects and the like.Accordingly, numerous other designs and constructions are possiblewithout departing from the spirit and scope of the invention.

With respect to the cylinder, a further key aspect of the invention thattranscends any particular design and construction is that ambient airmay be admitted through a hollow tube, which also acts as the pistonrod, and then through a valve at the bottom of the piston itself intothe bottom chamber of the cylinder during the upward stroke of thepiston. This air is then compressed during the downward stroke of thepiston. In some embodiments, the air so compressed in the bottom chamberis next transferred to the top chamber of the cylinder, above thepiston, and further compressed as the piston moves upward in thecylinder. Or in other embodiments, the compressed air in the bottomchamber may be fed directly to the pressure holding tank and the topchamber may be fed ambient air through a valve at the top of the pistonwhile the piston is on its downward stroke. The ambient air in the topchamber would then be compressed on the piston's upward stroke, while atthe same time additional ambient air is again fed into the bottomchamber to be compressed on the downward stroke. In either case, the aircompressed in the top chamber may then be transferred to the pressureholding tank, just as was the air from the bottom chamber during theprevious phase of the cycle. The valve configurations and the locationsof both the inlets and outlets for the two chambers of each cylinder mayvary depending on the design and application, exemplary ones of whichare described further below. In any such cylinder design, depending onthe particular embodiment of the compressor, the air compressed in afirst cylinder may be transferred to further cylinders for additionalstages of compression. The additional cylinders may be connected to thesame drive mechanism as the first cylinder or to a separate drivemechanism. It will be appreciated that by compressing air on theupstroke and the down stroke in each cylinder, the useful work done bythe piston is effectively doubled for the same work by the motor incycling the piston through its stroke. Moreover, by introducing ambientair into the cylinder's top and bottom chambers in alternating fashionthrough the piston rod itself and valves on the respective top andbottom sides of the piston, the air is caused to move through thecylinder at all stages of compression in a more laminar fashion. Theseeffects coupled with the relatively longer or larger volume stroke andintermittent speed of the piston thus enable the air to effectively be“squeezed” rather than “slammed,” providing numerous additional benefitsin terms of the performance, cost, and maintenance of the cylinders andthe rest of the compressor. These and other advantages of the presentinvention will be further apparent with reference to the following moredetailed description and the accompanying drawing figures. Firstdescribed below are various embodiments of the drive mechanism andoverall compressor structure with general reference to the operation ofthe piston itself, with further more detailed descriptions of the designand operation of various exemplary piston configurations then following.

Referring to FIGS. 1 and 2, there is shown a first exemplary embodimentof an improved air compression apparatus embodying the principles of thepresent invention. In this exemplary embodiment, the compressor 100 isan assembly comprised essentially of the following major parts: apressure tank 102, a motor 104, a belt or geared speed reduction ordrive mechanism 110 to reduce the number of revolutions per minute of aflywheel 120, a crankpin 122 attached to the flywheel 120, an intakeblock 126 rotatably attached to the crankpin 122, a cylinder 130, apiston assembly 140 moving within the cylinder 130, a valve mechanism(not shown) integrated with the piston assembly 140 to control thepassage of air flowing into the cylinder 130, check valves 180 at thetop and bottom of the cylinder 130 to control the passage of air to thepressure tank 102, a hollow tube 170 rigidly attached to the intakeblock 126 at one end and the piston 140 at the opposite end and actingas a piston rod, a gland (not shown) at the top of the cylinder 130 toprovide an airtight seal about the outside surface of the hollow pistonrod 170, a pivot arm 150 pivotably attached to both the base of thecylinder 130 and some distance away to a shaft 152 rigidly mounted tothe compressor's frame 106, and a guide bar 154 rigidly attached to thepivot arm 150, which moves in response to movement of the crankpin 122through a bearing 124 on the end of the crankpin 122 located within aslot 156 in the guide bar 154 and so causes the cylinder 130 to move inan oscillating fashion, shifting both vertically and horizontally, asthe top of the cylinder 130 follows the crankpin 122 through connectionof the pivot rod 170 to the intake block 126 and the bottom of thecylinder 130 shifts in response to movement of the pivot arm 150 inconnection with the movement of the guide bar 154, more about which willbe said below. Additional minor parts may include tubing, bearings,screws, nuts, bolts, washers, clips, bushings, springs, retainers,connectors, filters, and other small parts as necessary to hold themajor parts in proper relationship to each other and to provide forefficient movement of the various moving parts.

Regarding movement of the cylinder 130 in response to the cooperativemovement of the flywheel 120, the guide bar 154 and the pivot arm 150,it will be appreciated that during use the cylinder 130 is effectivelycaused to move dynamically, both vertically and laterally, rather thanbeing static or even pivoted about a single fixed point. As the motor104 drives the flywheel 120 on its shaft 125, the flywheel 120 in turnmoves the crankpin 122 radially. Because the crankpin 122 is configuredsuch that its free end is positioned within a slot 156 in the guide bar154, preferably through a roller bearing 122 or the like, movement ofthe flywheel 120 results in corresponding movement of the guide bar 154.This movement of the guide bar 154 then translates to movement of thelower end of the cylinder 130, again, both vertically and laterally, asthe pivot arm 150 to which the guide bar 154 is rigidly affixed pivotsabout the shaft 152 rigidly mounted to the compressor's frame 106,thereby causing the cylinder 130 to pivot about the pivot pin 158installed in the pivot arm 150 offset from the pivot shaft 152. At thesame time, the radial movement of the flywheel 120, and thus thecrankpin 122, also results in vertical and lateral movement of thepiston rod 170, and corresponding oscillation of the top end of thecylinder 130, through rigid connection of the piston rod 170 to theintake block 126 and connection of the intake block 126 to the crankpin122. Accordingly, it will be appreciated by those skilled in the artthat the oscillating movement of the cylinder 130 is caused by thecorresponding movement of the guide bar 154 as driven by the crankpinthrough the rotation of the flywheel 120. As such, both ends of thecylinder are effectively dynamically floating within the exemplarycompressor mechanism, whereby the cylinder is articulated with little orno lateral forces acting on the piston rod during its operation, or asit cycles through its strokes. Put another way, the guide bar isconfigured to absorb most or all of the lateral forces resulting fromthe driving movement of the flywheel and crankpin, so that the onlyforces effectively acting on the piston rod during all phases of thecompressor's operation are along the piston rod's axis so as to move thehollow piston rod up and down within the cylinder, with effectively noside load on the piston or piston rod during operation of thecompressor. It will be further appreciated, then, that such constructionand operation greatly reduces the wear of the piston itself, the glandsealing the top of the cylinder about the piston rod, and the othermoving parts in the assembly, minimizes the heat build up in thecylinder, and practically eliminates the debris entering the air streamwithin the cylinder. The amount of debris may be further reduced by theselection and use of self-lubricating materials so as to eliminatelubricants from within the inner workings of at least the moving partsof the mechanism that directly contact the air stream. By way ofexample, the gland through which the piston rod operates is preferably abronze bushing, the ring or rings about the circumference of the pistonmay be made of Teflon®, and the piston rod itself may be constructed ofa highly polished steel, and the inside wall of the cylinder may becarbon coated. It will be appreciated, though, that numerous other suchmaterials now known or later developed may be employed in the presentinvention. In turn, this reduced wear on the piston and other suchmoving parts results in increased efficiency, longer life, and lessdown-time and repair costs for the compressor as well as improvedcleanliness of the compressed air produced. The geometry of the guidebar and pivot arm is merely exemplary, as is the distance from the pivotshaft to the point where the cylinder is pivotably mounted to the pivotarm, such variables being capable of virtually an infinite number ofcombinations to produce different performance values of the compressordepending on the application. Furthermore, the slot may be varied inshape utilizing various curves or angles, as explained more fully belowwith respect to an alternative embodiment, to more precisely control theextent and timing of the oscillations of the cylinder relative to thecrank, such motion, again, acting to gear the effective speed of thepiston relative to the cylinder and thereby to increase or decrease theeffective amount of leverage applied by the motor against the compressedload of air within the cylinder. Similarly, the guide bar itself may begenerally linear, or the free end thereof and, accordingly, the slot,may be slightly cocked to further achieve the desired variable speed ofthe piston while at the same time causing increased leverage to beapplied to the compressed air through the piston, including helping thepiston and cylinder to slow down at the apex of the flywheel where themost compressive work is being done. Relatedly, while the crankpin isshown as being mounted on the flywheel so as to extend perpendicularlytherefrom, it may also be mounted at varying angles to the flywheel andinclude an additional pivot arm at the free end of the crankpin, betweenthe intake block and the guide bar slot, in order to provide further orexaggerated attenuation and variable-speed effects of the piston rod,as, for example, in high pressure applications. Whether the crankpin isgenerally perpendicular to the flywheel, and thus the guide bar, or atsome other angle, it is also contemplated that the bearing or other suchdevice at the end of the crankpin or secondary pivot arm be capturedwithin the slot through low friction discs, such as Teflon®, having adiameter larger than the width of the slot and mounted to the crankpinitself on opposite sides of the guide bar. It is further contemplatedthat a Teflon® or other such sleeve be installed within the slot in theguide bar to further reduce friction during operation of the compressor.It will thus be appreciated that a virtually infinite number ofgeometrical and mechanical variations on the exemplary embodiment of thecompressor shown and described can be employed without departing fromthe spirit and scope of the invention.

In terms of the other structural elements of the exemplary compressordesign of the present invention, a vertical pressure tank 102 maygenerally be employed, as illustrated in the accompanying drawings. Thesize and orientation of the tank 102, the flywheel 120, and the one ormore cylinders 130, and, in turn, the stroke length of each of thecylinders, will essentially dictate the other geometrical and mechanicalconsiderations, including the size and shape of a protective housing(not shown) positioned about the working parts of the compressor 100.The tubing 182 between the one or more cylinders and the tank ispreferably flexible so as to accommodate the oscillation of eachcylinder 130 during operation, though other types of rigid andsemi-rigid tubing with rotating connectors may also be possible. Personsacquainted with the art will understand that various embodiments mayemploy variations in the configuration of the assembly within the scopeof this invention. Some embodiments may employ a single piston orfurther pairs of pistons, driven by the same crank or by a further crankor cranks in a parallel structure, for additional compression. In someembodiments some or all of the moving parts that come in contact withthe compressed air may be constructed of self-lubricating material, suchas Teflon® piston rings or carbon composites, so that no oil isintroduced into the air stream and further minimizing debris. Mostembodiments of the compressor design will employ extended length,relatively small diameter cylinders, on the order of 1¾ to 2 inches (4.5to 5 cm), with the crank driving the pistons through a relatively longstroke, on the order of 8 inches (20 cm), at relatively low revolutionsper minute, on the order of 150 to 200 rpm, though it will beappreciated by those skilled in the art that numerous other cylinder andpiston geometries and crank speeds may be employed depending on theapplication without departing from the spirit and scope of theinvention. It will be further appreciated that the exemplary structureproviding for variable rate of leverage against the compressed load ofair enables a higher output of compressed air with less demand of powerfrom the motor, as well as no need for means of heat dissipation due tothe low friction, low speed, smooth operation of the one or morepistons. An exemplary motor that may be installed in the air compressionapparatus of the present invention is a single phase, 6 hp electricmotor rated at 3450 rpm at 120 volts and 60 cycles, though it will beappreciated that numerous power sources both now known and laterdeveloped may be employed without departing from the spirit and scope ofthe invention. In any event, the resulting compressor invention is alsothen generally characterized by a relatively low manufacturing cost,reduced maintenance and longer life through such benefits as reducedwear on the moving parts and even load on the drive motor duringoperation, and relatively cleaner compressed air output, higher pressurecapability, quieter operation, and improved overall efficiency.

In another exemplary embodiment the pivot arm and guide bar may bereplaced by a cam and cam follower or a yoke arrangement (not shown) atthe shaft 125 holding the crank 120, along with a drive rod attached toa pivot shaft (not shown) at the top of the cylinder. In thisembodiment, as the crank turns, the cam or yoke mechanism drives thedrive rod, which moves the cylinder up and down relative to the positionof the crank, such motion acting to alter the effective motion of thepiston relative to the cylinder and thereby to increase or decrease theeffective amount of leverage applied by the apparatus against thecompressed load of air within the cylinder.

In use, the drive mechanism 110 reduces the rotational speed of themotor shaft 108 to the desired rotational speed for the crank 120 so asto drive the piston 140 at the desired reduced number of strokes perminute. The rotational motion of the crankpin 122, connected to thepiston rod 170 through the intake block 126 and moving in a slot 156 inthe guide bar 154, causes a lateral oscillating motion of the cylinder130, as described above. In addition to the cylinder's lateral movement,the cylinder is caused to oscillate vertically relative to the crank 120as the crank rotates, either by attachment to a pivot arm 150 offset adistance from the pivot shaft 152, or by a cam or yoke arrangement (notshown) with a rod attached both to the cam or yoke and to the pivotpoint of the cylinder. The vertical oscillating motion of the cylinderassembly 130 relative to the crank 120 causes a controlled variation inthe speed of the piston 140 relative to the cylinder 130 and to thecompressed air load within the cylinder, providing for a controlledvariation in the leverage applied by the crank 120 against thecompressed air load. As the piston 140 is retracted toward the top ofthe cylinder 130 during part of the rotation of the crank 120, the valve(not shown) at the bottom of the piston 140 is pulled open by the actionof a vacuum created in the bottom chamber of the cylinder 130, so thatambient air then passes through the hollow piston rod 170 and open valveinto the bottom chamber. When the piston 140 has reached the top of itsstroke, the valve at the bottom of the piston is closed, and the air inthe bottom chamber is compressed by the downward movement of the piston140 and driven through a check valve 180 into the pressure tank 102 orinto the chamber in the cylinder 130 above the piston 140. During thedownward travel of the piston 140, a valve 142 at the top of the pistonadmits air through the hollow piston rod 170 into the upper chamber. Asthe piston 140 moves upward, new air is drawn into the lower chamber andthe air in the upper chamber is compressed and passed either into thepressure storage tank 102 or into another cylinder (not shown) forfurther compression in a similar manner. Based on this operation of anexemplary embodiment of the compressor, it will be appreciated that themechanism is capable of effectively producing a variable rate ofcompression in four general phases. In a first phase, say, when thepiston 140 is retracted toward the top of the cylinder 130 on itsupstroke, as when the crankpin 122 is moving toward the top, or apex, ofthe flywheel 120 in a counter-clockwise direction through the effectivequadrant of the flywheel between 3:00 and 12:00, or between ninety andzero degrees, the flywheel 120, and thus the crankpin 122, the pistonrod 170, and the piston 140 itself, is beginning to slow down as thepiston 140 is nearing the top of its stroke. This slow-down enables themotor 104 to apply increased torque with relatively less additional workby the motor due to the cooperation of the reduction mechanism 110 andthe other mechanical structure and principles at work in driving theflywheel 120, thereby yielding a nice, smooth “squeezing” of the airduring the final part of the upstroke compression in the upper chamberof the cylinder 130. Essentially at the apex, the air in the upperchamber has reached its maximum compression for the cylinder 130 and isdischarged through the upper chamber's check valve 180 as describedabove. Then, once the crankpin 122 has passed beyond the apex and ismoving through roughly the second quadrant of the flywheel 120 betweenthe 12:00 and 9:00 positions, a second phase of operation is begunwherein the flywheel 120, and thus the crankpin 122, the piston rod 170,and the piston 140 itself, is speeding back up as the relatively easier,initial work of compression is being done in the lower chamber andambient air is being introduced into the evacuated upper chamber as thepiston 140 is on its down stroke. Next, a third phase of operation isinitiated as the crankpin 122 continues to move counter-clockwise andenters the third quadrant of the flywheel 120 between 9:00 and 6:00where, similar to the first phase, as the piston 140 is advanced towardthe bottom of the cylinder 130 on its down stroke, the flywheel 120, andthus the crankpin 122, the piston rod 170, and the piston 140 itself, isbeginning to again slow down as the piston 140 is nearing the bottom ofits stroke. Once more, this slow-down results in greater torque appliedby the motor 104 and reduction mechanism 110 without a significantincrease in the load on the motor as it drives the flywheel 120,resulting in a smooth and efficient “squeezing” of the air during thefinal part of the down stroke compression in the bottom chamber of thecylinder 130. When the air has reached its maximum compression in thelower chamber, it is then discharged through a check valve 180 or passedinto the upper chamber for further compression on the piston's upstroke,as described above. Finally, once the crankpin 122 has movedcounterclockwise into the fourth quadrant of the flywheel 120 between6:00 and 3:00, the fourth phase of operation analogous to the oppositesecond phase is begun wherein the flywheel 120, and thus the crankpin122, the piston rod 170, and the piston 140 itself, is again speedingback up as the relatively easier, initial work of compression is beingdone now in the upper chamber and ambient air is once more beingintroduced into the evacuated lower chamber as the piston 140 continueson its upstroke. This four-phase, intermittent speed and pressure cycleis simply repeated to efficiently compress air from ambient conditionsto a desired higher pressure. It will be appreciated by those skilled inthe art that the drive mechanism and the other geometry of thecompressor can be just as easily set up so that the flywheel effectivelyturns clockwise. As such, the descriptions of the operation of theflywheel throughout are to be understood as being merely exemplary. Onceagain, further speed and pressure variance during the cycle is achievedby the simultaneous, coordinated, dynamic movement of the cylinder 130itself through its pivoted connection on the pivot arm 150 linkagewithin the mechanism. With reference to the preceding generaldescription of the operation of an exemplary compressor through thesefour phases, then, it is to be understood that each of the angularpositions about the flywheel referred to are for explanation of theprinciples of operation of the present invention only and that the exactpositions and transitions of each of the four general phases ofoperation are not so limited, such positions and transitions beingdictated by and varying with the particular application and thegeometrical and mechanical design and orientation of the movingstructural elements of a particular version of the compressor of thepresent invention. In the context of the operation of a compressorhaving a flywheel, it will be further appreciated that the flywheel isessentially a gear that is part of an overall reduction mechanism alongwith a motor 104, a drive pulley 112 installed on the motor shaft 108 soas to be substantially coplanar with the flywheel 120, a belt 114 or thelike engaging the drive pulley 112 and the flywheel 120, and one or moretensioners 116 or pulleys to take the slack out of the belt 114 duringoperation. In an exemplary embodiment of the compressor wherein thepiston has a ten-inch stroke, driving the flywheel at an average speedof about 150 rpm would be typical, though numerous speeds are possible,again, depending on the application and, accordingly, the strokerequired. Thus, the flywheel's operation, at least in this embodiment,is not as much a factor of its inertia as its rotational speed andtorque translating to the axial forces acting along the piston rod so asto move the piston up or down within the cylinder. Moreover, because themajority of the moving parts are preferably constructed of aluminum orlightweight plastic, there is very little inertial effect, particularlyat such relatively low rpm, such that the compressor operates with verylittle shaking or noise. Noise may be additionally reduced by mountingthe motor on a resilient support to dampen vibration. Further, becausethe motor works hardest when it needs to during the final portion ofeach compression stroke or phase and works less when it doesn't need to,as when the piston has completed its up or down stroke and has startedback in the opposite direction, it will be appreciated that the powerrequirements of the motor and the wear and tear on the motor are greatlyreduced in the compressor design of the present invention.

Turning to FIGS. 3-6, there is shown an alternative embodiment of thecompressor 200 of the present invention wherein the slot 256 in theguide bar 254 is “S-shaped” and the guide bar itself has a slightlydifferent profile. As shown, the remaining structure of the compressoris essentially the same as that of the above-described exemplaryembodiment, including a flywheel 220 with crankpin 222, an intake block226 connected between the crankpin 222 and the top of the piston rod270, a pivot arm 250 pivotally connected to both the frame 206 of thecompressor and, at some distance away, the bottom end of the cylinder,and a guide bar 254 rigidly mounted to the pivot arm 250 and at itsopposite free end dynamically linked to the crankpin 222 throughlocation of a bearing 224 or the like of the crankpin within the slot256 formed in the guide bar 254. The S-shaped slot then furtheraccentuates the principle at work in the previously described exemplaryembodiment of the invention. Particularly, with reference to FIGS. 4-6,it will be appreciated by those skilled in the art that the curvature ofthe S-shaped slot 256 and the resulting accentuated movement of theguide bar 254, and thus the cylinder 230, as the guide bar 254 followsthe crankpin 222 through the travel of the crankpin's bearing 224 withinthe slot 256 furthers the advantages achieved through the compressordesign of the present invention of dynamically shifting the cylinder 230and varying the speed of the piston (not shown) therein accordinglythroughout the cycle. This is further evident with reference to thedrawing figures, which indicate that while the guide bar 254 is rigidlyattached to the pivot arm 250 at the bottom of the cylinder 230 andtravels with the cylinder through its lateral oscillations, it does notnecessarily do so identically. This is true of each of the embodiments,but is exaggerated through the use of an S-shaped slot 256 or the like.That is, as the flywheel 220 rotates, at some points during the cyclethe cylinder 230 will essentially be “ahead” of the guide bar 254, as,for example, in a first phase shown in FIG. 4, while at other times thecylinder 230 will essentially “lag” behind the guide bar 254, as in athird phase shown in FIG. 6. It will be appreciated that the net effectof the cylinder's leading and following the guide bar as described andshown is greater attenuation, or more extreme oscillation, of thecylinder within the same basic geometry and overall movement of theflywheel and guide bar, such as, for example, in a typical eight-inchstroke configuration. It will also be appreciated with reference toFIGS. 4-6 that pivot arm 250 pivots about the pivot shaft 252 as theguide arm 254 rigidly mounted to the pivot arm 252 follows the crankpin222. Accordingly, the relative movement of the cylinder 230 is caused byits pivotable connection effectively at its upper end with the crankpin222 through the piston rod 270 and intake block 226 and effectively atits lower end with a pivot pin 258 mounted to the pivot arm 250. Withrespect to the S-shaped slot alternative embodiment, then, as for otherembodiments, it is to be understood that numerous modifications to thesize and shape of the slot and the other components of the compressorare possible without departing from the spirit and scope of theinvention.

Referring now to FIGS. 7-12, there is shown in six phases of operationyet another exemplary embodiment of the compressor 300 of the presentinvention wherein the flywheel 320 is “lobed,” or roughly elliptical inshape. The elliptical flywheel 320 is formed with an outer rim 329defining the flywheel's elliptical profile as having a major diameterand a minor diameter. In the exemplary embodiment, opposing spokes 328are formed substantially along the major and minor diameters so as toconnect a hub 327 rotatably installed on the flywheel shaft 324 to theouter rim 329, though it will be appreciated that this is not necessaryand so is merely exemplary. As shown, much of the remaining structure ofthe compressor 300 is like that of the above-described exemplaryembodiments, including the installation of a crankpin 322 on theflywheel 320 and an intake block 326 connected between the crankpin 322and the top of the piston rod 370. As explained more fully below, thecrankpin 322 is mounted on the flywheel 320 within a first quadrantdefined as an arcuate segment of the flywheel 320 between the majordiameter and the minor diameter, or between the 12:00 and 3:00 positionsas the flywheel is oriented with its major diameter substantiallyhorizontal. For clarity and ease of explanation, and as an alternativeembodiment of the present invention, the exemplary lobed flywheel doesnot include a pivot arm pivotally connected to both the frame of thecompressor and the bottom end of the cylinder or a guide bar rigidlymounted to the pivot arm and at its opposite free end dynamically linkedto the crankpin, though it will be appreciated that this structure, orany other such structure such as, for example, a cam or yokearrangement, and its resultant advantages through articulating thecylinder both horizontally and vertically may also be employed in thislobed flywheel compressor design. Rather, the cylinder 330 is pivotallyinstalled at its bottom end to a pivot pin 358 mounted to the frame 306of the compressor 300. Generally, with respect to the lobed flywheelconfiguration, it will be appreciated that the variation of speed andtorque achieved as the flywheel 320 is driven by the motor 304 operatingat a constant speed, and the resulting variation in the speed andpressure of the piston itself (not shown) through the linkage of thepiston rod 370 to the flywheel 320 through the crankpin 322, againproduces smooth and efficient air compression. Particularly, in thefirst phase shown in FIG. 7, when the piston is retracted toward the topof the cylinder on its upstroke, as when the crankpin 322 is movingtoward the top, or apex, of its travel on the flywheel 320 in acounterclockwise direction, the flywheel 320, and thus the crankpin 322,the piston rod 370, and the piston itself, is beginning to slow down asthe piston is nearing the top of its stroke. Specifically, at about thisposition in the cycle the lobed flywheel is positioned radially suchthat its major axis is roughly horizontal. Because the overall geometryis set up in this exemplary embodiment such that the belt 314 drivingthe flywheel 320 is substantially vertical when the flywheel is in thisposition, it will be appreciated that at this stage in the cycle themotor 304 is acting through the largest radial distance with respect tothe axis of the flywheel 320 so as to apply the largest amount of torqueand turn the flywheel 320 effectively at or near its slowest speed.Accordingly, the compressor geometry is configured such that at thisstage in the flywheel's rotation, the piston is at or near the top ofits stroke so that this slow-down and the resulting increased torqueapplied by the motor and reduction mechanism in driving the flywheelproduces a nice, smooth “squeezing” of the air during the final part ofthe upstroke compression in the upper chamber of the cylinder. As withthe other exemplary embodiments of the compressor of the presentinvention, it will be appreciated that the motor is able to provideincreased torque, and thus increased pressure through the piston rod tothe piston, without doing an appreciable amount of additional work.Therefore, again, the geometrical and mechanical relationships set up inthe compressor help or enable the motor to do more work with lesseffort, and hence to operate more efficiently. Right at the peak of themovement of the piston rod 370, as in the second phase of movement shownin FIG. 8, the air in the upper chamber has reached its maximumcompression for the cylinder and is discharged through the upperchamber's check valve as previously described. Then, once the crankpin322 has passed beyond this apex point and is beginning to move thepiston through its down stroke, as in the third phase of operation shownin FIG. 9, the flywheel 320, and thus the crankpin 322, the piston rod370, and the piston itself, is speeding back up as the relativelyeasier, initial work of compression is being done in the lower chamberand ambient air is being introduced into the evacuated upper chamber asthe piston is on its down stroke, again, more about which is said below.It will be appreciated that this increased speed and reduced torque isachieved as the effective or working diameter of the flywheel 320 isgradually reduced by shifting from the lobed flywheel's major diametertoward its minor diameter during its rotation; that is, as the workingdiameter becomes relatively smaller, the flywheel turns faster at alower torque. As shown in FIG. 10, then, during an intermediate fourthphase of the operation of the exemplary lobed flywheel compressorembodiment, the flywheel 320 is continuing its counterclockwise rotationas its effective diameter decreases until the point shown where theminor diameter of the flywheel is generally horizontal. As such, thiswould effectively be the smallest working diameter of the flywheel 320,or the point at which speed is roughly greatest and torque is roughlyleast. This is acceptable and, in fact, desirable during this phase asno real work is yet needed in essentially “gathering” the ambient air.Transitioning from this fourth phase to the position of the flywheel 320indicated in FIG. 11 results in the flywheel slowing down, similar tothe first phase of FIG. 7, as its working diameter again shifts backtoward the major diameter of the lobed flywheel. Thus, as the piston isnow advanced toward the bottom of the cylinder on its down stroke, theflywheel 320, and thus the crankpin 322, the piston rod 370, and thepiston itself, is beginning to again slow down as the piston is nearingthe bottom of its stroke. Once more, this slow-down results in greatertorque applied by the motor and reduction mechanism in driving theflywheel, and ultimately the piston, at a relatively slower speed, so asto again produce a smooth “squeezing” of the air during the final partof the down stroke compression in the bottom chamber of the cylinder.When the air has reached its maximum compression in the lower chamber,basically at the position of the piston in the fifth phase shown in FIG.11, it is then discharged through a check valve or passed into the upperchamber for further compression on the piston's upstroke, as describedabove. Finally, once the crankpin 322 has moved counterclockwise beyondthis lowest position in the direction shown in the sixth phase of FIG.12, the flywheel 320, and thus the crankpin 322, the piston rod 370, andthe piston itself, is again speeding back up as the flywheel 320 is oncemore rotating in orientation toward its minimum working diameter as therelatively easier, initial work of compression is being done now in theupper chamber and ambient air is once more being introduced into theevacuated lower chamber as the piston continues on its upstroke. Thisalternative intermittent speed and pressure cycle is simply repeated toagain efficiently compress air from ambient conditions to a desiredhigher pressure. Once more, further speed and pressure variance duringthe cycle may be achieved by the simultaneous, coordinated, dynamicmovement of the cylinder body itself through its pivoted connection on apivot arm linkage within the mechanism and corresponding attenuationthrough a guide arm working in concert with the crankpin, or throughother such structure, as explained above with respect to other exemplaryembodiments of the present invention. With reference to the precedinggeneral description of the operation of the alternative exemplary lobedflywheel compressor through its various phases, then, it is to beunderstood that each of the positions about the flywheel referred to orshown are for explanation of the principles of operation of the presentinvention only and that the exact positions and transitions of each ofthe phases of operation are not so limited, such positions andtransitions being dictated by and varying with the particularapplication and the geometrical and mechanical design and orientation ofthe moving structural elements of any particular version of thecompressor of the present invention, particularly in the event that aguide bar and pivot arm mechanism or other such structure is added tothe structure shown. A double tensioner configuration involving atensioner pulley 316 and an idler pulley 317 as shown may be employed soas to take slack variation out of the belt 314 or other such drive meansduring all phases of operation of the lobed flywheel design as abovedescribed.

Referring to FIG. 13, another exemplary embodiment of the aircompression apparatus 400 of the present invention is shown wherein theflywheel 420 is again roughly elliptical in shape, formed with an outerrim 429 defining the flywheel's elliptical profile as having a majordiameter and a minor diameter. In this exemplary embodiment, opposingspokes 428 are formed substantially along the major diameter while onespoke 417 is formed along the minor diameter so as to so as to connectthe hub 427 rotatably installed on the flywheel shaft 424 to the outerrim 429. A radially-outwardly projecting fastening plate 419 to whichthe crankpin 422 is mounted is formed on the flywheel outer rim 429laterally offset from the drive belt 414. A fourth spoke 418 is formedon the flywheel 420 offset from the minor diameter so as to also connectthe hub 427 to the outer rim 429 so as to be substantially continuouswith the fastening plate 419 and give support thereto, though it willagain be appreciated that the structure and arrangement of any of thespokes is merely exemplary and that numerous other arrangements arepossible without departing from the spirit and scope of the invention.With continued reference to FIG. 13, much of the remaining structure ofthe compressor 400 is like that of the above-described exemplaryembodiments, including the installation of the crankpin 422 on theflywheel 420 and an intake block 426 connected between the crankpin 422and the top of the piston rod 470 to facilitate passage of ambient airinto the hollow piston rod as explained in more detail below. Similar tothe embodiment of FIGS. 7-12, specifically, the fastening plate 419, andthus the crankpin 422, is mounted on the flywheel 420 substantiallywithin a first quadrant defined as an arcuate segment of the flywheel420 between the major diameter and the minor diameter. The cylinder 430is again shown as pivoting about a pivot pin 458 mounted to the frame406 of the compressor 400. Once more, as a further alternativeembodiment of the present invention, the elliptical flywheel compressor400 may also include a pivot arm pivotally connected to both the frameof the compressor and the bottom end of the cylinder, a guide barrigidly mounted to the pivot arm and at its opposite free enddynamically linked to the crankpin, or a cam or yoke arrangement so asto further articulate the cylinder both horizontally and vertically. Amotor 404 having a drive pulley 412 installed on its shaft againcooperate with a tensioner pulley 416 and an idler pulley 417 topositively drive the elliptical flywheel 420 through the drive belt 414during operation of the compressor 400. As compared to the ellipticalflywheel 320 of FIGS. 7-12, it will be appreciated that the ratio of themajor diameter to the minor diameter in the present exemplary embodimentis essentially greater, resulting in relatively greater speed and torquevariance during operation of the compressor 400 based on the workingdiameters of the flywheel 430 alone during its rotation. Once more, itwill be appreciated by those skilled in the art that numerousconfigurations of the flywheel, elliptical or otherwise, may be employedin the compressor to suit particular applications and performancecriteria without departing from the spirit or scope of the presentinvention.

Turning to FIG. 14, there is shown yet another exemplary embodiment ofthe air compression apparatus 500 of the present invention wherein theflywheel 520 is roughly elliptical in shape, again formed with an outerrim 529 defining the flywheel's elliptical profile as having a majordiameter and a minor diameter. In this exemplary embodiment, opposingspokes 528 are formed substantially along the major diameter while onespoke 518 is formed along the minor diameter so as to connect the hub527 to the outer rim 529. A fourth spoke 519 is formed on the flywheel520 offset from the minor diameter so as to also connect the hub 527 tothe outer rim 529 and to extend radially substantially within a firstquadrant defined as an arcuate segment of the flywheel 520 between themajor diameter and the minor diameter. As shown, the crankpin 522 ismounted on the fourth spoke 519 so as to again position the crankpin 522within the first quadrant, or out of phase with both the major and minoraxes of the elliptical flywheel 520. It will again be appreciated thatthe structure and arrangement of any of the spokes and even the preciselocation of the crankpin 522 on the flywheel 520 are merely exemplaryand that numerous other arrangements are possible without departing fromthe spirit and scope of the invention. With continued reference to FIG.14, two masses 515 are symmetrically located within the outer rim 529substantially along the major diameter to add inertial effect to theflywheel 520. Other locations and types and sizes of such weights arepossible. Much of the remaining structure of the exemplary compressor500 is like that of the above-described exemplary embodiments, includingthe installation of the crankpin 522 on the flywheel 520 and an intakeblock 526 connected between the crankpin 522 and the top of the pistonrod 570 to facilitate passage of ambient air into the hollow piston rodas further explained below. The cylinder 530 is again shown as pivotingabout a pivot pin 558 mounted to the frame 506 of the compressor 500,though the cylinder is 530 is depicted as being relatively shorter andlarger in diameter than the other cylinders shown and described above.More about this particular cylinder structure and operation is saidbelow, but it will be appreciated that in such flywheel or crank-drivencompressors, the effective stroke length is essentially dictated by thelocation of the crank pin on the crank and the degree of actuation ofthe cylinder body. Here, it will be appreciated that the crankpin 522 isshown positioned on the spoke 519 of the flywheel 520 a relatively shortdistance from the hub 527, and hence the flywheel shaft (not shown). Inthe exemplary embodiment, the cylinder has a diameter of roughly 3¼ to3½ inches (8¼ to 9 cm) and the radial location of the crankpin 522translates to an approximately 1½ to 2 inch (4 to 5 cm) stroke. It willbe appreciated by those skilled in the art that such a cylinderarrangement may be driven at relatively higher speeds, on the order of500 to 700 rpm, for example, due to the reduced inertial effectsresulting from essentially reduced attenuation of the cylinder andpiston assembly. Once more, though not shown, it will be appreciatedthat as a further alternative embodiment of the present invention, theelliptical flywheel compressor may also include a pivot arm pivotallyconnected to both the frame of the compressor and the bottom end of thecylinder, a guide bar rigidly mounted to the pivot arm and at itsopposite free end dynamically linked to the crankpin, or a cam or yokearrangement so as to further articulate the cylinder both horizontallyand vertically so as to potentially increase the stroke length. A motor504 having a drive pulley 512 installed on the motor shaft 508 againcooperates with a tensioner pulley 516 and an idler pulley 517 topositively drive the elliptical flywheel 520 through the drive belt 514during operation of the compressor 500. As compared to the ellipticalflywheel 520 of FIGS. 7-12, it will be appreciated that the ratio of themajor diameter to the minor diameter in the present exemplary embodimentis essentially less, resulting in relatively less speed and torquevariance during operation of the compressor 500, which effect it will beappreciated is offset due to the increased inertial effects caused, inpart, by the addition of symmetrical masses 515 to the flywheel 520 andthe increased speed at which the flywheel may potentially be driven.Once more, it will be appreciated by those skilled in the art thatnumerous configurations of the flywheel, elliptical or otherwise, may beemployed in the compressor in combination with various cylinderarrangements to suit particular applications and performance criteriawithout departing from the spirit or scope of the present invention.

Turning now to FIG. 15, there is shown a still further alternativeembodiment of the air compression apparatus 600 of the present inventionwherein the variable speed and pressure of the piston is achievedthrough a chain drive and cam follower mechanism. Two gears or sprockets620, 621 operate in tandem to drive a chain or belt 614 to which a camfollower 622 is connected along a substantially oval path. In apreferred embodiment, the sprockets comprise a driving sprocket 620 andan idler sprocket 621 in spaced apart relationship such that the centersof the sprockets define a centerline parallel to and offset from theaxis of the cylinder 630. The cam follower 622 is located and travelswithin a slot 656 formed in a track arm 654 that is rigidly connected tothe intake block 626 at an intermediate point along its length andsubstantially at a free end to a sliding bushing 652 operating along afixed guide rod 650 secured between opposite attachment blocks 651.Preferably, the guide rod is parallel to and offset from the centerlineof the sprockets 620, 621 opposite the cylinder 630. The intake block626 is rigidly connected to the hollow piston rod 670 as in the otherexemplary embodiments of the invention and is again formed with at leastone passage (not shown) to allow ambient air to pass into the piston rod670, whereby the piston rod 670 is effectively rigidly attached to thetrack arm 654. The generally diagonal or angled orientation of the trackarm 654 relative to the substantially vertically oriented members of theassembly such as the piston rod 670 and guide rod 650, preferably at anacute angle of between zero and ninety degrees relative to the guiderod, serves to provide increased pressure on the piston (not shown)during the high compression phase of operation, as explained more fullybelow. Both the guide rod 650 and the one or more cylinders are mountedto the compressor's frame 606 or pressure tank (not shown) usingconventional attachment blocks or the like, though it is to beunderstood that the cylinder may also be pivotally or dynamicallyaffixed in any of the exemplary ways shown and described in connectionwith the other exemplary embodiments of the present invention or usingany other such means now known or later developed in the art. The drivemechanism, including the sprockets 620, 621 are also preferablyinstalled on the frame 606 or the tank. Relatedly, while the inlet andoutlet valves to the cylinder and, accordingly, the tubing leading tothe tank, are not shown, it will be appreciated that they can beinstalled in numerous ways without departing from the spirit and scopeof the invention. Though the chain drive, cylinder, and guide rod areeffectively oriented vertically, it will also be appreciated thatvirtually any spatial orientation of these and the other components ofthe alternative chain drive compressor design are possible. As describedmore fully below, the substantially oval path of the chain drive coupledwith the diagonal slot and its orientation relative to the cylinderresults in the desired varied speed and pressure of the piston.

In operation, then, as the chain drive 614 moves, whether clockwise orcounterclockwise as driven by the pair of sprockets 620, 621, the camfollower 622 operates within the slot 656 of the track arm 654 so as toeffectively shift the track arm 654 up and down vertically, resulting invaried speed and pressure of the piston rod 670 through its rigidconnection to the track arm 654 via the intake block 626. It is assumedfor the purpose of the following more detailed explanation that thechain drive 614 is being driven clockwise and that the cylinder employedis “double-acting” as described elsewhere herein. In a first phase ofoperation wherein the cam follower 622 is positioned adjacent the upperdrive sprocket 620 so that it is entering effectively a first quadrantbetween the 9:00 and 12:00 positions, or between two hundred seventy andthree hundred sixty degrees, it will be appreciated that the piston isbeing pulled upwardly, or is on its upstroke, as the cam follower 622continues in a clockwise direction on the chain drive 614 such that thepiston is nearing the top of its stroke, or the maximum compression ofthe air in the cylinder's upper chamber. At this time, the speed of thepiston is also slowing down as the cam follower 622 is moving on thechain 614 around the circumference of the upper sprocket 620 so as toshift toward increased horizontal displacement, as opposed to verticaldisplacement, which, in turn, results in reduced vertical displacementof the track arm 654 and, hence, the intake block 626, the piston rod670, and the piston itself. Accordingly, it will be further appreciatedthat while the movement of the piston is slowing, the effective force onthe piston is increasing due to the leverage effect achieved through thecam follower 622 moving more and more along the slot 656, rather thanagainst it, so as to take advantage of the fundamental “ramp” deviceknown and used in various mechanical arts. As such, the track armmechanism 654 enables the cam follower 622 to do more work in liftingthe piston during its final phase of compression with the same effort,or, put another way, to apply more force without appreciably any morework by the motor (not shown) driving the chain drive 614 through thepair of sprockets 620, 621. It will be appreciated by those skilled inthe art that numerous other configurations of the track arm, both interms of its orientation and the size and shape of its slot, takingadvantage of and even further exploiting the effect of this mechanicalprinciple are possible without departing from the spirit and scope ofthe invention. During this first phase of operation, then, the resultingslow-down of the piston while at the same time increasing the force itis applying to the column of air in the cylinder's upper chamber againresults in a nice, smooth “squeezing” of the air during the final partof the piston's upstroke. When the cam follower 622 reaches the apex ofits vertical travel around the upper sprocket 620, or about the 12:00position, the air in the upper chamber has reached its maximumcompression for this cylinder and is discharged through the upperchamber's check valve as described herein elsewhere in connection withother exemplary embodiments of the present invention. Then, in a secondphase of operation, once the cam follower 622 has passed beyond the apexand is moving through the second quadrant of the upper sprocket 620roughly between the 12:00 and 3:00 positions, it is shifting back toincreased vertical displacement as its horizontal displacementeffectively about the radius of the upper sprocket 620 is completed.This increasing vertical displacement yields a corresponding increasingvertical displacement and speed of the track arm 654. Accordingly, theintake block 626, the piston rod 670, and the piston itself are speedingback up as the relatively easier, initial work of compression is beingdone in the lower chamber of the cylinder 630 and ambient air is beingintroduced, or “gathered,” into the evacuated upper chamber as thepiston is on its down stroke. This low-work, “air-gathering” secondphase continues as the cam follower 622 travels the substantially linearsection of the chain 614 effectively between opposite tangential pointson the right sides of the respective upper and lower sprockets 620, 621.Next, a third phase of operation is initiated as the cam follower 622arrives at roughly the 3:00 position on the lower idler sprocket 621 andso enters what is effectively the third quadrant of the chain drive 614,between the lower sprocket's 3:00 and 6:00 positions. In this thirdphase, then, analogous to the first phase, the piston is now beingpushed downwardly as the cam follower 622 continues in a clockwisedirection on the chain drive 614 such that the piston is nearing thebottom of its stroke, or the maximum compression of the air in thecylinder's lower chamber. Once more, during this phase, the speed of thepiston is also slowing down as the cam follower 622 is moving on thechain 614 around the circumference of the lower sprocket 621 so as toshift toward increased horizontal displacement, as opposed to verticaldisplacement, again resulting in reduced vertical displacement of thetrack arm 654 and, hence, the intake block 626, the piston rod 670, andthe piston itself. Again, while the movement of the piston is slowing,the effective force on the piston is increasing due to the leverageeffect achieved through the cam follower 622 moving effectively along amechanical ramp formed by the slot 656, enabling the cam follower 622 todo more work in pushing the piston downward during its final phase ofcompression with the same essential effort by the motor, resulting in asmooth and efficient “squeezing” of the air during the final part of thedown stroke compression in the bottom chamber of the cylinder 630. Whenthe air has reached its maximum compression in the lower chamber, it isthen discharged through a check valve or passed into the upper chamberfor further compression on the piston's upstroke, as describedpreviously with other embodiments. Finally, in a fourth basic phase ofoperation analogous to the above-described second phase, once the camfollower 622 has passed beyond the low-point of the lower sprocket 621,or roughly the 6:00 position, and is moving through effectively thefourth quadrant of the chain drive 614 between roughly the 6:00 and 9:00positions on the lower sprocket 621, the cam follower 622 is shiftingback to increased vertical displacement as its horizontal displacementeffectively about the radius of the lower sprocket 621 is completed.Once again, this increasing vertical displacement yields a correspondingincreasing vertical displacement and speed of the track arm 654, and,hence, the intake block 626, the piston rod 670, and the piston itselfare speeding back up as the relatively easier, initial work ofcompression is being done in the cylinder's upper chamber and ambientair is being “gathered” into the now evacuated lower chamber as thepiston is again on its upstroke. This low-work, “air-gathering” fourthphase continues as the cam follower 622 travels the substantially linearsection of the chain 614 effectively between opposite tangential points,or 9:00 positions, on the left sides of the respective upper and lowersprockets 620, 621. This four-phase, intermittent speed and pressurecycle is simply repeated to efficiently compress air from ambientconditions to a desired higher pressure. Once again, further speed andpressure variance during the cycle may be achieved by the simultaneous,coordinated movement of the cylinder body itself through a pivoted ordynamic connection to the mechanism rather than the rigid connectionshown.

With reference to the preceding general description of the operation ofan exemplary chain drive compressor 600 of the present invention throughfour basic phases, then, it is to be understood that each of thegeometrical and mechanical elements and features discussed are forexplanation of the principles of operation only and that the inventionis not so limited. Rather, it will be appreciated that numerous changesto the geometry shown and described are possible without departing fromthe spirit and scope of the invention. For example, it is to beunderstood that though it is preferable to have the axis of the pistonrod substantially aligned vertically over the centerline of thedual-sprocket chain drive so as to get essentially the same work ofcompression on both the upstroke and down stroke of the piston, this isnot necessary and, depending on the application, may be less desirablein view of other design considerations. One instance where this may bedesirable would be the use of the chain drive and track arm to operatetwo cylinders simultaneously in parallel, each offset vertically fromthe centerline of the chain drive on opposite sides. Or, as a furtherexemplary alternative, a second cylinder can be actuated by the singlechain drive and track arm by extending co-linearly with, but in theopposite direction from, the first cylinder shown. In this embodiment,both cylinders could operate effectively along the centerline of thechain drive and could even share a common intake block. Whether one ormore cylinders are driven, a single guide rod offset to one side of thechain drive, as shown, or a second guide rod offset on the opposite sideof the chain drive to provide additional lateral stability may also beemployed. Additionally, it will be appreciated by those skilled in theart that the chain drive embodiment of the compressor of the presentinvention may be particularly suited to high volume or high pressurecontexts due to the relative ease with which the size or stroke of theone or more cylinders can be increased, and may be so modifiedaccordingly. That is, a longer-stroke piston can be driven by the chaindrive compressor by simply increasing the length of the guide rod orrods and the effective length of the chain drive, as by moving thesprockets further apart or even adding additional sprockets, pulleys,tensioners, tracks or the like to stabilize the linear sections of thechain or belt between the upper and lower sprockets. Additional,spaced-apart sliding bushings on each of the guide rods and rigidlyconnected to the track arm could be used to further stabilize themechanism in such longer-stroke applications. The increased stroke alsoeffectively increases the accuracy or precision of the derived airpressure due to the increased stroke ratio, or the total length thepiston travels, and thus the volume of air compressed, compared to thelength of the high-compression phase at or near the completion of the upand down strokes. It will be further appreciated that this increase inpiston stroke length, and hence capacity of the compressor, isattainable by effectively increasing only the length of the mechanism,not its width or depth to any real extent. However, as a further exampleof alternative embodiments for the chain drive compressor design, largeror smaller sprockets can also be employed as needed based on theapplication and pressure requirements. Ultimately, movement of the chain614 about the sprockets 620, 621 translates into oscillating linearmovement of the track arm 654 and simultaneous axial displacement of thepiston body (not shown) within the cylinder 630 as acted on by thepiston rod 670 rigidly mounted to the track arm 654 through the intakeblock 626. Accordingly, it is to be understood that the variousembodiments of the chain drive compressor are merely exemplary, and thatnumerous other configurations may be employed without departing from thespirit or scope of the invention.

Referring to FIGS. 16 and 17, another alternative air compressorapparatus 700 of the present invention is shown as generally having twocylinders 730, 731 installed on a frame 706 in a substantially alignedoffset arrangement. The first cylinder 730 is formed with a first lowercylinder wall 732 and has a first piston body 740 sealingly and slidablyinstalled therein so as to form a first upper chamber 734 above thefirst piston body 740 and a first lower chamber 736 below the firstpiston body 740. The second cylinder 731 is formed with a second lowercylinder wall 733 and has a second piston body 741 sealingly andslidably installed therein so as to form a second upper chamber 735above the second piston body 741 and a second lower chamber 737 belowthe second piston body 741. A first piston rod 770 and a second pistonrod 771 are rigidly connected at respective adjacent ends to the drivemechanism 710. The first piston rod 770 has a first hollow bore (notshown) and at least one first breathing hole 774 communicating betweenthe first hollow bore and the ambient air. The first piston rod 770passes through the first cylinder 730 and the first upper chamber 734and is connected at a first piston end opposite the drive mechanism 710to the first piston body 740 so that the first hollow bore selectivelycommunicates with the first lower chamber 736. Similarly, the secondpiston rod 771 has a second hollow bore 773 and at least one secondbreathing hole 775 communicating between the second hollow bore 773 andthe ambient air. The second piston rod 771 passes through the secondcylinder 731 and the second upper chamber 735 and is connected at asecond piston end opposite the drive mechanism 710 to the second pistonbody 741 so that the second hollow bore 773 selectively communicateswith the second lower chamber 737. At least one first escape passage 738is formed within the first cylinder 730 so as to selectively communicatebetween the first upper chamber 734 and the first lower chamber 736, thefirst escape passage 738 having a first longitudinal length greater thanthe thickness of the first piston body 740. Likewise, at least onesecond escape passage 739 is formed within the second cylinder 731 so asto selectively communicate between the second upper chamber 735 and thesecond lower chamber 737, the second escape passage 739 having a secondlongitudinal length greater than the thickness of the second piston body741. A first lower piston valve 742 is installed on the first pistonbody 740 so as to selectively seal the first lower chamber 736 from thefirst hollow bore. A second lower piston valve 743 is installed on thesecond piston body 741 so as to selectively seal the second lowerchamber 737 from the second hollow bore 773. A first check valve 783 isinstalled in the first cylinder 730 so as to communicate with the firstupper chamber 734 and a second check valve 784 is installed in thesecond cylinder 731 so as to communicate with the second upper chamber735. Similarly, a first one-way valve 780 is installed in the firstcylinder 730 in fluid communication with the first upper chamber 734 anda second one-way valve 781 is installed in the second cylinder 731 influid communication with the second upper chamber 735. More about theoperation of these valves is said below with respect to the operation ofthe compressor 700. Air lines 782 are then connected to the first andsecond one-way valves 780, 781, whereby movement of the drive mechanism710 effectively in a first direction acts on the first piston rod 770 tocause the first piston body 740 to travel toward the first lower chamber736, drawing ambient air into the first upper chamber 734 through thefirst check valve 783 while closing the first lower piston valve 742 andcompressing the air in the first lower chamber 736 until the firstpiston body 740 nears the first lower cylinder wall 732 such that the atleast one first escape passage 738 is temporarily no longer sealed bythe first piston body 740 so as to allow the compressed air to pass fromthe first lower chamber 736 through the at least one first escapepassage 738 and into the first upper chamber 734, where the compressedair then mixes with the ambient air for further compression when thepiston 740 begins its travel in the opposite direction. Simultaneously,movement of the drive mechanism 710 in the first direction acts on thesecond piston rod 771 to cause the second piston body 741 to traveltoward the second upper chamber 735, closing the second check valve 784and further compressing the air in the second upper chamber 735 whileopening the second lower piston valve 743 to allow ambient air to bedrawn through the at least one second breathing hole 775 and the secondhollow bore 773 into the second lower chamber 737. Similarly, movementof the drive mechanism 710 in an opposite second direction acts on thefirst piston rod 770 to cause the first piston body 740 to travel towardthe first upper chamber 734, closing the first check valve 783 andfurther compressing the air in the first upper chamber 734 while openingthe first lower piston valve 742 to allow ambient air to be drawnthrough the at least one first breathing hole 774 and the first hollowbore into the first lower chamber 736. Simultaneously, movement of thedrive mechanism 710 in the second direction acts on the second pistonrod 771 to cause the second piston body 741 to travel toward the secondlower chamber 737, drawing ambient air into the second upper chamber 735through the second check valve 784 while closing the second lower pistonvalve 743 and compressing the air in the second lower chamber 737 untilthe second piston body 741 nears the second lower cylinder wall 733 suchthat the at least one second escape passage 739 is temporarily no longersealed by the second piston body 741 so as to allow the compressed airto pass from the second lower chamber 737 through the at least onesecond escape passage 739 and into the second upper chamber 735 to mixwith the ambient air for further compression when the piston 741 beginsits travel again in the first direction. It will be appreciated by thoseskilled in the art that while a standard check valve is employed in thisexemplary embodiment for the purpose of introducing ambient air into thefirst and second upper chambers of the respective cylinders, upperpiston valves as disclosed herein allowing for ambient air to beintroduced through the hollow piston rods into the upper chambers as thepistons travel toward the lower chambers may also be employed.

As best shown in FIG. 17, the drive mechanism 710 comprises a piston rodmounting block 726 mounted to the respective adjacent ends of the firstand second piston rods 770, 771 so as to rigidly support the first andsecond piston rods 770, 771 in a substantially coaxial arrangement. Thefirst and second breathing holes 774, 775 are positioned along therespective first and second piston rods 770, 771 so as to be clear ofthe piston rod mounting block 726. A yoke block 754 is rigidly mountedto the piston rod mounting block 726. The yoke block 754 is formed withan outwardly-opening yoke channel 756 at an angle between zero andninety degrees relative to the piston rod mounting block 726, theoperation of which is explained below. A cam pulley 720 is mounted tothe frame (not shown) so as to rotate about a cam pulley shaft (notshown), the cam pulley having a cam follower 722 projecting therefromoffset from the cam pulley shaft and oriented so as to extend into andengage the yoke channel 756. A drive pulley 712 is installed on a driveshaft 708 of the motor 704 so as to be substantially coplanar with thecam pulley 720, and a drive belt 714 is then configured to engage thedrive pulley 708 and the cam pulley 720 so that torque from the motor704 is transmitted to the cam pulley 720 through the drive belt 714,whereby rotational movement of the cam pulley 720 translates intooscillating linear movement of the piston rod mounting block 726 andsimultaneous axial displacement of the first and second piston bodies740, 741 within the respective first and second cylinders 730, 731 asacted on by the respective first and second piston rods 770, 771 rigidlymounted within the piston rod mounting block 726, as explained morefully below.

In operation, then, as the cam pulley 720 rotates, whether clockwise orcounterclockwise as driven by the motor 704 and drive pulley 712 throughthe belt 714, the cam follower 722 operates within the yoke channel 756of the yoke block 754 so as to effectively shift the piston rod mountingblock 726 up and down vertically, resulting in varied speed and pressureof the respective piston rods 770, 771 through their rigid connection tothe piston rod mounting block 726. For the purposes of the followingexplanation, it is assumed that the cam pulley 720 is rotatingcounterclockwise as viewed from the front as shown in FIG. 16. In afirst phase of operation of the compressor 700 the cam follower 722 ispositioned within the yoke channel 756 at a location effectively withina first and fourth quadrant of the cam pulley 720 between the 6:00 and12:00 positions, or between zero and one hundred eighty degrees, it willbe appreciated that the piston rod mounting block 726 is being pulledupwardly, such that the first piston body 740 is on its upstroke and thesecond piston body 741 is on its down stroke, whereby the first lowerpiston valve 742 is closed so as to compress the air in the first lowerchamber 736 while an effective vacuum is created in the first upperchamber 734 so as to pull ambient air in through the first check valve783. At the same time, the second lower piston valve 743 is opened so asto draw ambient air into the second lower chamber 737 while compressingthe air in the second upper chamber 735. As the cam pulley 720 continuesits counterclockwise rotation the cam follower 722 continues to engagethe yoke channel 756 and shift the piston rod mounting block 726 furtherupward, continuing the compression in the first lower chamber 736 andthe second upper chamber 735. This continues until the first piston body740 nears the first lower cylinder wall 732, at which time the speed ofthe piston rod mounting block 726 is slowing down as the cam follower722 is continuing its arcuate path as it moves with the cam pulley 720such that the cam follower 722 is shifting toward increased horizontaldisplacement, as opposed to vertical displacement, which, in turn,results in reduced vertical displacement of the yoke block 754 and,hence, the piston rod mounting block 726, the piston rods 770, 771, andthe pistons 740, 741 themselves. Accordingly, it will be appreciatedthat while the movement of the pistons 740, 741 is slowing, theeffective force on the pistons is increasing due to the leverage effectachieved through the cam follower 722 moving more and more along theslot 756, rather than against it, so as to take advantage of thefundamental “ramp” device, again, known and used in various mechanicalarts. As such, the yoke block 754 enables the cam follower 722 to domore work in lifting the pistons during their final phase of compressionwith the same effort, or, put another way, to apply more force withoutappreciably any more work by the motor 704 driving the cam pulley 720.It will be further appreciated by those skilled in the art that numerousother configurations of the yoke block, both in terms of its orientationand the size and shape of its slot, taking advantage of and even furtherexploiting the effect of this mechanical principle are possible withoutdeparting from the spirit and scope of the invention. During this firstphase of operation, then, the resulting slow-down of the pistons 740,741 while at the same time increasing the force they are applying to thecolumns of air in the respective first lower chamber 736 and secondupper chamber 735 again results in a nice, smooth “squeezing” of the airduring the final part of the pistons' stroke. When the cam follower 722reaches the apex of its vertical travel on the cam pulley 720, or aboutthe 12:00 position, the air in the first lower chamber 736 has reachedits maximum compression for this chamber and at that time passes throughthe exposed first escape passage 738 and into the first upper chamber734 for further compression when the piston body 740 starts in theopposite direction as explained below. At the same time, the air in thesecond upper chamber 735 has also reached its maximum compression forthis cylinder 731 and is then discharged through the one-way valve 781.In a second phase of operation, once the cam follower 722 has passedbeyond the apex and is moving through the second and third quadrantsbetween the 12:00 and 6:00 positions, or between zero and one hundredeighty degrees, it will be appreciated that the piston rod mountingblock 726 is now being pulled downwardly through the cam follower'sengagement with the yoke channel 756 of the yoke block 754, such thatthe first piston body 740 is on its down stroke and the second pistonbody 741 is on its upstroke, whereby the first lower piston valve 742 isopened so as to draw ambient air into the first lower chamber 735 whilecompressing the air in the first upper chamber 734 and the second lowerpiston valve 743 is closed so as to compress the air in the second lowerchamber 737 while an effective vacuum is created in the second upperchamber 735 so as to pull ambient air in through the second check valve784. As the cam pulley 720 continues its counterclockwise rotation thecam follower 722 continues to engage the yoke channel 756 and shift thepiston rod mounting block 726 further downward, continuing thecompression in the first upper chamber 734 and the second lower chamber737 and drawing ambient air into the first lower chamber 736 and secondupper chamber 735. This continues until the second piston body 741 nearsthe second lower cylinder wall 733, at which time, the speed of thepiston rod mounting block 726 is slowing down as the cam follower 722 iscontinuing its arcuate path as it moves with the cam pulley 720 suchthat the cam follower 722 is again shifting toward increased horizontaldisplacement, as opposed to vertical displacement, which, in turn,results in reduced vertical displacement of the yoke block 754 and,hence, the piston rod mounting block 726, the piston rods 770, 771, andthe pistons 740, 741 themselves. Accordingly, it will be appreciatedthat while the movement of the pistons 740, 741 is slowing, theeffective force on the pistons is again increasing due to the leverageeffect achieved through the cam follower 722 moving more and more alongthe slot 756, rather than against it. As such, the yoke block 754enables the cam follower 722 to do more work in pushing the pistonsduring their final phase of compression with the same effort, or, putanother way, to apply more force without appreciably any more work bythe motor 704 driving the cam pulley 720. During this second phase ofoperation, then, the resulting slow-down of the pistons 740, 741 whileat the same time increasing the force they are applying to the columnsof air in the respective first upper chamber 734 and second lowerchamber 737 again results in a nice, smooth “squeezing” of the airduring the final part of the pistons' stroke. When the cam follower 722reaches the low point of its vertical travel on the cam pulley 720, orabout the 6:00 position, the air in the first upper chamber 734 hasreached its maximum compression for this cylinder 730 and is thendischarged through the one-way valve 780. At the same time, the air inthe second lower chamber 737 has also reached its maximum compressionfor this chamber and at that time passes through the exposed secondescape passage 739 and into the second upper chamber 735 to mix with theambient air therein for further compression when the piston body 741starts in the opposite direction as explained above when the camfollower 722 moves past the low point and back into the first phase ofoperation. This two-stage, intermittent speed and pressure cycle issimply repeated to efficiently compress air from ambient conditions to adesired higher pressure. Once again, further speed and pressure varianceduring the cycle may be achieved by the simultaneous, coordinatedmovement of the cylinders themselves through a pivoted or dynamicconnection to the mechanism rather than the rigid connection shown. Itwill be appreciated by those skilled in the art that the structure andgeometry shown is merely exemplary and that numerous otherconfigurations can be practiced without departing from the spirit andscope of the invention.

Based on the foregoing, it will be appreciated that with respect to atleast one exemplary embodiment, the air compression apparatus can begenerally described as an improved multi-stage gas compressor. Theprinciple at work in the exemplary embodiment compressor 700 describedabove and shown in FIGS. 16 and 17 is an assembly made up in part ofvalved pistons moving within cylinders, each driven by a shaped pathwithin a yoke. Passages in and around the pistons transfer the gas fromone chamber to another in increasing stages of compression. Again, thoseskilled in the art will appreciate that numerous other mechanicalarrangements are possible for achieving the multi-stage air compressiondescribed. The individual chambers within the system may be eitherdynamic or static. The volume of each dynamic chamber is less than thatof the dynamic chamber preceding it in the compression cycle by acalculated amount in order to provide for a stepped increase in pressurefrom the supply or ambient pressure to the higher pressure in theexternal holding tank. The dynamic chambers also change in volumedynamically, in response to movement of the yoke, to enhance themovement of gas from one chamber to another and to provide for increasedefficiency in the application of power from the motor. The staticchambers provide holding and transitional space for the gas as it movesthroughout the system.

In the preferred embodiment shown, two cylinders 730, 731 act inparallel, with both cylinders independently compressing gas into theexternal holding tank (not shown) through the air lines 782. In anotherpreferred embodiment (not shown), the cylinders act in series, with thesecond cylinder receiving compressed gas from the first cylinder andcompressing it further. The compressor 700 is an assembly made up of thefollowing major parts, depending on the particular embodiment: a caseenclosing the whole assembly (not shown), including several chambers andsub-chambers connected by gas passages, a shaft 708 driven by a motor704, a yoke driver 720 either attached rigidly to the shaft or driven bya drive pulley 712 mounted on the shaft 708 through a belt 714, a yoke754, a path 756 of particular shape and design within the yoke 754, oneor more track rollers 722 moving within the path 756 in the yoke 754, apartly hollow piston rod 770, 771 attached rigidly to mounting block 726attached rigidly to the yoke 754 so as to engage each track roller 722through the yoke path 756, a partly hollow piston 740, 741 rigidlyattached to each piston rod 770, 771, an inertial valve 742, 743 withineach piston 740, 741, a cylinder 730, 731 enclosing each piston 740,741, escape air passages 738, 739 connected at each cylinder 730, 731,in some preferred embodiments a spring-loaded automatic check valve (notshown) at the entrance to each cylinder escape air passage 738, 739, agland encircling each piston rod 770, 771, and a spring-loaded automaticcheck valve 780, 781 at the gas exit point of each sub-chamber 734, 735.The gland may be comprised of a linear ball bearing in combination witha rod seal. Check valves or further piston inertial valves or the likemay be employed in introducing ambient air into the upper chambers ofeach cylinder as explained elsewhere. Additional minor parts may includebearings, screws, clips, bushings, springs, retainers, connectors,tubing, filters and other small parts as necessary to hold the majorparts in proper working relationship to each other, to provide forefficient movement of the various moving parts, and to provide forcontrolled passage of gas from one chamber to another. The path 756within the yoke 754 may be shaped in any one of several different ways,depending on the particular embodiment. The purpose of the shaped path756 is to apply a controlled amount of mechanical leverage to the piston740, 741 proportional to the pressure applied to the piston 740, 741 bythe compressed gas, as explained above. That is, the piston movesfaster, with a lower degree of leverage, when the pressure is low, andslower, with a higher degree of leverage, when the pressure is high.This proportional variation in leverage, again, provides for moreefficient utilization of the power drawn from the motor and for reducedvibration and heat. In some embodiments, the path in the yoke may beconstructed so as to provide for a different rate and extent of pistontravel in different cylinders. The piston rod 770, 771 is hollow from apoint above the mounting block 726 to the hollow part of the piston 740,741 and collects and transports the gas to be compressed by the pistonto which it is connected. The piston 740, 741 has a hole extending fromits top to the upper end of the piston rod 770, 771. This hole in thepiston 740, 741 is provided at the upper end with an inertial valve 742,743 which opens to admit gas when the piston begins moving downward andcloses to compress the gas when the piston begins moving upward.Controlled passage is provided for the gas compressed by the piston toescape from the lower chamber 736, 737 into the sub-chamber 734, 735.The gas in the sub-chamber 734, 735 is further compressed as the piston740, 741 moves downward in the respective cylinder 730, 731 as explainedabove. In one preferred embodiment, with the cylinders working inseries, the gas compressed in the first sub-chamber is passed through atransition chamber to the hollow piston rod of the second cylinder wherethe compression cycle is repeated above and below the piston in order toachieve a higher pressure output. In another preferred embodiment asshown in FIGS. 16 and 17, with the two cylinders 730, 731 working inparallel, each cylinder takes in gas at ambient pressure and each of thetwo cylinders compresses gas independently, each expressing gas directlyinto the external holding tank, which results in a greater volume of gasbeing compressed to a relatively lower initial output pressure,depending, of course, on the geometries of the cylinders. In a preferredembodiment, the two pistons 740, 741, with their connecting rods 770,771 and the yoke 754, form a rigid structure which moves as a singlestructural unit, so that little side load is present at the pistons.Other embodiments may employ further pairs of pistons, driven by thesame yoke or by additional yokes in a parallel structure for additionalcompression. Preferably all the moving parts which come in contact withthe gas are constructed of self-lubricating material so that no oil isintroduced into the gas stream as it is being compressed. A furtherenhancement to address noise reduction during operation of thecompressor is shown in FIG. 16. A woven or mesh sleeve 790 may beinstalled substantially concentrically within each hollow piston rod770, 771 so as to essentially position its outer wall in contact orsubstantially adjacent to the inner wall of the piston rods 770, 771 soas to effectively interrupt its smooth surface. As such, it will beappreciated that the sleeve 790 will serve to dampen sound wavestraveling up the hollow piston rods 770, 771 during operation, and thusfurther reduce noise. Those skilled in the art will appreciate that sucha woven or mesh sleeve or any other such tubular member having desirableacoustic damping characteristics may be installed within the hollowpiston rod of any variation of the present invention.

It will be appreciated by those skilled in the art that the variousstructural and geometrical configurations of the drive mechanism of theair compression apparatus of the present invention are merely exemplaryand that numerous such drive systems can be employed in achievingvariable-speed, variable-pressure actuation of the one or more pistonsoperably connected to the drive mechanism so as to yield efficient,clean, and quiet air compression as described herein. With respect tothe drive mechanism alone, it will be appreciated, specifically, thatefficiency gains are due, in part, to running the motor and crank, yokeor other drive linkage at a relatively slower average speed and atvaried speed so that effectively lower speed and higher pressure aretransmitted to the one or more pistons when they are doing the greatestamount of work in compressing the air or gas and higher speed and lowerpressure are transmitted to the one or more pistons when they are doingless work. Relatedly, the relatively slow, variable speed of the movingparts results in improved power usage of the motor and less heat buildup in the system, further improving the efficiency. Moreover, by each ofthe drive mechanisms shown and described serving to effectively applypressure to the one or more pistons substantially along the respectivepiston rod, there is little to no side load on the pistons themselves asthey move within the cylinder, further reducing heat build-up and alsoserving to reduce the wear on the moving parts and, thus, the amount ofcontaminants in the compressed air output. Accordingly, it is to beunderstood that numerous other designs of the drive mechanism beyondthose exemplary embodiments shown and described are possible withoutdeparting from the spirit and scope of the invention.

The one or more cylinders employed in compressors according to thepresent invention may take on various configurations as well, again,depending on the application, numerous examples of which are describedin more detail below. Several novel cylinder designs have beenconceived, as shown in the drawings, capable of cooperating with themechanical and operational advantages achieved through structure such asin the exemplary embodiments shown and described, which yield arelatively longer working stroke or larger compressed volume of eachpiston along with coordinated variance in the speed of the piston duringits stroke, so as to ultimately produce smoother and more efficientcompression. Specifically, an added operational benefit provided by thevarious pistons according to the present invention is the introductionof air into the cylinder through a hollow piston rod and valves aboveand below the piston itself, though it will be appreciated that a singlevalve either above or below the piston may be employed so as to form asingle- or multi-stage cylinder, as described, for example, with respectto the embodiment of FIGS. 16 and 17. Where the cylinder is configuredto be double-acting as by having valves on the top and bottom of thepiston, for example, this results in compressing the air on both theupstroke and the down stroke in each cylinder, so as to effectivelydouble the useful work done by the piston as it cycles through itsstroke. This type of piston design also serves to move air through thecylinder at all stages of compression in a more laminar fashion. Thatis, it will be appreciated by those skilled in the art that introducingambient air into the cylinder through the hollow piston rod and thenthrough valves located effectively on or about the upper and lowersurfaces of the piston enables the air to enter the respective chambersboth immediately adjacent to the working surface of the piston andgenerally in the direction the piston will be traveling on itscompression stroke. This results in the ambient air effectively beingpushed along and squeezed toward its maximum compression, rather thanbeing “slammed” or run into by the piston at some intermediate point inthe stroke. Then, when the compressed air is to be evacuated from thecylinder, it is preferably done so at or near the “top,” or highcompression section, of each chamber. In this way, the air never reallyhas to reverse direction between the time it is introduced into eachchamber and when it exits. It will be appreciated that these featurestranslate to lower heat build-up and wear of the cylinder's internalmoving parts and increases the efficiency in operation. Again, theseeffects coupled with the relatively larger volume and intermittent speedof the piston can further enable the air to effectively be “squeezed”rather than “slammed,” providing numerous additional benefits in termsof the performance, cost, and maintenance of the cylinders and thecompressor. With respect to the valves and other parts of the cylinder,spring-loaded automatic check valves, which open and close in responseto the direction and pressure of the air flow, are preferably providedat the air exit point of each chamber to prevent any backward movementof compressed air through the system. In an alternative preferredembodiment, breathing chambers are provided at the exit points of eachchamber so effectively stage the compressed air as it evacuates thecylinder while still preventing backflow, yielding further benefits inoperation as described below. The hollow piston rods are preferably madeof a high-strength material, such as high-grade steel, polished smoothso as to move freely, with minimal friction and wear, through a gland.This gland provides a wall of separation between the air in the upperchamber and the ambient air by sealing about the outside surface of thepiston rod. In some embodiments two or more cylinders may be provided inseries, with the air being fed at increasing pressures from chamber tochamber, until the final chamber delivers the compressed air to theoutput pressure tank. Thus, persons familiar with the art may construct,within the principles of this invention, various embodiments applicableto high-volume or high-pressure air compression, encompassing a broadvariety of specialty compressors for various types of applications.

Turning to FIGS. 18-21, there is shown a first exemplary embodiment aircompression cylinder 230 of the present invention as potentiallyemployed in at least compressor systems such as those shown anddescribed with respect FIGS. 1-13, though it is noted that theembodiment of the cylinder 130 of FIGS. 1 and 2 employs a slightlydifferent intake block 126 than the intake block 226 shown in FIG. 18.Generally, the cylinder 230 has an annular wall 231, an upper end 232and an opposite lower end 233. The upper and lower ends 232, 233 may beinstalled within the annular wall 231 by a fastener such as a machinescrew, by welding, through a press- or interference-fit, or through anyother such means now known or later developed in the art. Depending onthe assembly technique, an o-ring may be seated within a circumferentialgroove formed about the upper and lower ends 232, 233 so as topositively seal the joint between the annular wall 231 and therespective upper and lower ends 232, 233. Exit valves 280, 281 lead fromthe respective upper and lower ends 232, 233 to the air lines 282 andtank 202 (FIG. 3). In the exemplary embodiment, upper and lower one-wayvalves 280, 281 are installed in the ends 232, 233 in fluidcommunication with the upper chamber and lower chambers 234, 235 so asto allow air flow therethrough only out of the cylinder 230 whilepreventing any backflow, as is known in the art. A piston assembly 240is operably connected to the drive mechanism 210 (FIG. 3) and configuredto move within the cylinder 230 mounted to the frame 206 (FIG. 3) asdescribed above with respect to the numerous exemplary embodiments ofthe present invention. Turning to FIG. 19, the piston assembly 240comprises a piston body 241 having an upper piston wall 244 and anoffset lower piston wall 245 joined about an annular piston wall 246 soas to define at least one radially-outwardly-opening circumferentialpiston ring channel 260 in which at least one piston ring 262 isinserted so as to sealably and slidably contact the inside surface ofthe cylinder wall 231 during operation of the piston, more about whichis said below. The upper and lower piston walls 244, 245 may be integralwith the annular piston wall 246, as shown in FIG. 19, or may beinstalled thereon as separate components, as shown in other exemplaryembodiments of the invention, using any mechanical fastening technique,such as screws or other such fasteners, a weld, or a press-fit, both nowknown or later developed in the art. The piston body 241 so installedwithin the cylinder 230 thus forms an upper chamber 234 between thepiston body 241 and the upper end 232 of the cylinder 230 and a lowerchamber 235 between the piston body 241 and the lower end 233 of thecylinder 230. The piston body is further formed with a cavity 247substantially bounded by the upper and lower piston walls 244, 245 andthe annular piston wall 246 so as to be in selective communication withat least the lower chamber 235, though the cavity 247 is shown in theexemplary embodiment as selectively communicating with the upper andlower chambers 234, 235 in cooperation with the upper and lower pistonvalves 242, 243, the operation of which are explained more fully below.Connected to the piston body 241 is a piston rod 270 having a hollowbore 273 communicating between a drive end and a piston end, the driveend being connected to the drive mechanism 210 such that the hollow bore273 is in communication with ambient air. In the exemplary embodiment,this is accomplished by installing the drive end of the piston rod 270within an intake block 226 such that the bore 273 is able to communicatewith ambient air through an opening 227 formed in the intake block 226.The piston rod 270 passes through the cylinder 230 at its upper end 232,as through a gland (not shown) that sealingly and slidably engages theoutside surface of the piston 270, and then through the upper chamber234 so as to be connected at the opposite piston end to the piston body241. The piston rod has at least one opening formed thereinsubstantially at the piston end such that the hollow bore 273 is incommunication with the cavity 247. A lower piston valve 243 is installedon the piston body 241 so as to selectively seal the lower chamber 235from the cavity 247, while an upper piston valve 242 is installedadjacent to the piston body 241 so as to selectively seal the upperchamber 234 from the cavity 247. In this way, when the air line 282 isconnected to the cylinder 230 so as to communicate with both the upperchamber 234 and the lower chamber 235 through the respective upper andlower valves 280, 281, it will be appreciated that upward travel of thepiston body 241 as caused by the drive mechanism 210 (FIG. 3) actingthrough the piston rod 270 closes the upper piston valve 242 so as tocompress the air within the upper chamber 234 while opening the lowerpiston valve 243 to allow ambient air to enter the lower chamber 235through the hollow bore 273 of the piston rod 270, whereas downwardtravel of the piston body 241 as caused by the drive mechanism 210acting through the piston rod 270 opens the upper piston valve 242 andallows ambient air to be drawn through the piston rod bore 273 into theupper chamber 234 while closing the lower piston valve 243 to compressthe air in the lower chamber 235. Specifically, in the exemplaryembodiment of FIGS. 18-21, the cavity 247 comprises an upper piston bore248 formed in the upper piston wall 244 in communication with a lowerpiston bore 249 formed in the lower piston wall 245, the lower pistonbore 249 having an internal diameter substantially equivalent to theexternal diameter of the piston rod 270 such that the piston rod 270 isseated within the lower piston bore 249 so as to communicate therewiththrough the hollow bore 273. The upper piston bore 248 has an internaldiameter greater than the external diameter of the piston rod 270, sothat the piston rod 270 is formed with one or more cross-holes 274positioned therein so as to communicate between the hollow bore 273 andthe upper piston bore 248 and thereby allow for communication betweenthe upper and lower piston bores 248, 249 essentially through the hollowbore 273 of the piston rod 270. Regarding the lower piston valve 243, anoutwardly-opening annular channel is formed in the lower piston wall 245and a lower o-ring 266 is seated within the annular channel.Accordingly, in the exemplary embodiment, the lower piston valve 243comprises a lower valve disk 267 movably mounted on the piston body 241substantially adjacent to the lower piston wall 245 so as to selectivelycontact the o-ring 266 and seal the lower piston bore 249, and thus thehollow bore 273 from the lower chamber 235. Regarding the constructionof the upper piston valve 242, a collar 268 is slidably installed on thepiston rod 270 and formed with a shoulder on its lower end substantiallyadjacent to the upper piston wall 244 on which an upper o-ring 269 isseated so as to selectively contact the upper piston wall 244 or anoutwardly-opening countersink formed on the upper piston bore 248 so asto seal the upper piston bore 248 and, thus, seal the cavity 247 fromthe upper chamber 234. A keeper ring, shoulder, or other such mechanicaldevice may be installed on the piston rod 270 above the collar 268 so asto maintain the collar 268 along the piston rod 270 substantiallyadjacent to the piston body 241 during all stages of operation, asdescribed below.

Referring now to FIGS. 20 and 21, in operation, the piston body 241 isslidably moved up and down within the cylinder 230 during operation ofthe air compression apparatus of the present invention as describedherein. In a first stage of operation as shown in FIG. 20, the pistonassembly 240 including the piston body 241 and piston rod 270 is movingdownwardly in the direction of arrows 201. As such, the inertial and airpressure effects cooperate to close the lower piston valve 243 bycausing the lower piston disk 267 to shift vertically upwardly intocontact with the o-ring 266, thereby sealing off the hollow bore 273from the lower chamber 235. As shown, a flat wave spring incorporatedinto the structure securing the lower piston disk 267 in place adjacentto the lower piston wall 245 may help bias the lower piston diskupwardly. A coil spring or other such structure now know or laterdeveloped in the art may be employed instead, or, as in otherembodiments shown and described herein, no biasing means at all may beemployed. Also during the first stage of operation, the upper pistonvalve 242 is opened by the inertial and air pressure effects againcooperating to lift the collar 268 to unseat the o-ring from thecountersink formed about the upper piston bore 248. It will beappreciated that the vacuum air pressure effect, specifically, is causedby the immediately preceding stage of operation during which highpressure compressed air was evacuated from the upper chamber 234. Oncethe collar 268 has shifted upwardly as shown, inertial effects caused bythe rapidly descending piston 241 work to maintain the collar's offsetposition with respect to the upper piston wall 244. It will be furtherappreciated that the retaining ring 209 shown or other such structureserves to limit the movement of the collar 268 relative to the pistonbody 241 and keep it substantially adjacent to the upper piston wall244. In this stage, then, as shown by arrows 203, ambient air passingthrough the hollow bore 273 of the piston rod 270 passes through thecross-holes 274, the opening or upper bore 248 of the cavity 247, andinto the upper chamber 234. At the same time, because the lower pistonvalve 243 is closed through the engagement of the lower piston disk 267with the o-ring 266, further downward travel of the piston body 241serves to compress the air in the lower chamber 235. It will beappreciated that the more that pressure builds up in the lower chamber235, the greater the seal between the lower piston disk 267 and theo-ring 266, as the increasing pressure applies greater and greaterupward force against the lower piston disk 267. This process ofintroducing ambient air into the upper chamber 234 and compressing theair in the lower chamber 235 continues until the piston body 241 nearsthe bottom end 233 of the cylinder 230 as dictated by the structure andgeometry of the driving mechanism 210 discussed above with respect tovarious exemplary embodiments. Once the piston body 241 has reached itslowest position within the cylinder 230, it will again be appreciatedthat the air in the lower chamber 235 has effectively reached itsmaximum pressure and is at that time discharged from the lower chamber235 as described elsewhere herein. At that point, the piston 241 thentransitions to a second stage of operation during which it is travelingupwardly within the cylinder 230 as indicated by arrows 202 in FIG. 21.During this stage, it will again be appreciated that the inertial andair pressure effects cooperate to now close the upper piston valve 242by causing the collar 268 to shift downwardly as the piston body 241 ismoving rapidly upward, thereby seating the o-ring in the countersinkformed about the upper piston bore 248 to seal off the hollow bore 273from the upper chamber 234. At the same time, the lower piston valve 243is opened by the inertial and air pressure effects again cooperating topull the lower piston disk 247 downwardly and space it from the o-ring266. It will be appreciated that the vacuum air pressure effect,specifically, is caused by the immediately preceding stage of operationduring which high pressure compressed air was evacuated from the lowerchamber 235. Once the lower piston disk 267 has shifted downwardly asshown, inertial effects caused by the rapidly ascending piston 241 workto maintain the disk's offset position with respect to the lower pistonwall 245 and the o-ring 266, specifically. It will be furtherappreciated that the structure of the lower piston valve 243 serves toretain the lower piston disk substantially adjacent to the lower pistonwall 245 and that while a rigid plate mounted through screws, pegs, orother such fasteners is shown, numerous other mechanical means, nowknown or later developed, for maintaining the position of the lowerpiston disk 267 relative to the lower piston wall 245 may be employed.In this second stage, then, as shown by arrows 204, ambient air passingthrough the hollow bore 273 of the piston rod 270 passes out the end ofthe bore 273, through the opening that is the lower bore 249 and betweenthe lower piston disk 267 and the o-ring 266 into the lower chamber 235.At the same time, because the upper piston valve 242 is closed throughthe engagement of the o-ring 269 on the collar 268 with the countersinkof the upper bore 248 or with the upper piston wall 244 itself, furtherupward travel of the piston body 241 serves to compress the air in theupper chamber 234. It will again be appreciated that the more thatpressure builds up in the upper chamber 234, the greater the sealbetween the countersink and the o-ring 269, as the increasing pressureapplies greater and greater downward force against the collar 268 as thepiston 241 travels upward. This process of introducing ambient air intothe lower chamber 235 and compressing the air in the upper chamber 234continues until the piston body 241 nears the top end 232 of thecylinder 230 as dictated by the structure and geometry of the drivingmechanism 210 discussed elsewhere. Once the piston body 241 has reachedits highest position within the cylinder 230, it will again beappreciated that the air in the upper chamber 234 has effectivelyreached its maximum pressure and is at that time discharged from theupper chamber 234 as described. At that point, the piston 241 thentransitions back to the first stage of operation during which it istraveling downwardly within the cylinder 230 as shown in FIG. 20. Basedon the foregoing description of the cylinder 230 in operation, it willbe appreciated that the view shown in FIG. 19 with both the upper andlower piston valves 242, 243 open is essentially a static view of theconstruction for explanatory purposes and does not necessarily reflectthe positions of the moving parts of the assembly at any given stage ofoperation. It will also be appreciated that while the cavity 247 isshown as having an annular space between the opposite upper and lowerbores 248, 249, in this embodiment it is not necessary for theintroduction of ambient air through the piston rod 270 to either theupper or lower chambers 234, 235. As such, and for other reasons relatedto manufacturing and assembly, the piston body 241 could just as easilyhave been a solid, unitary construction with the upper and lower bores248, 249 formed therethrough, though it will be appreciated by thoseskilled in the art that removal of material, and thus weight, from thepiston 241 has other advantages during operation, particularly dependingon the size of the piston and the speed at which it is moving. Andwhether the piston body 241 is of unitary or modular construction, itwill also be appreciated that extending a portion of the annular pistonwall 246 or the upper piston wall 244 radially inwardly so as to engagethe outside surface of the piston rod 270 may be preferable in furthersupporting the piston rod within the piston body. Once more, it will beappreciated that the various components of the piston assembly,including the one or more components of the piston body and the pistonrod itself, may be assembled together to effectively form a single rigidstructure using techniques now know or later developed in the art.

Turning now to FIGS. 22-27, a further exemplary embodiment of the aircompression apparatus of the present invention is shown. Generally, thecylinder 830 has an annular wall 831, an upper end 832 and an oppositelower end 833. The upper and lower ends 832, 833 may be installed withinthe annular wall 831 as described above. Exit valves 880, 881 lead fromthe respective upper and lower ends 832, 833. A piston assembly 840 isoperably connected to the drive mechanism and configured to move withinthe cylinder 830 as described previously. Turning to FIG. 23, the pistonassembly 840 comprises a piston body 841 having an upper piston wall 844and an offset lower piston wall 845 joined about an annular piston wall846. Once more, the upper and lower piston walls 844, 845 may beintegral with the annular piston wall 846 or may be installed thereonusing any mechanical fastening technique now known or later developed.The piston body 841 so installed within the cylinder 830 thus forms anupper chamber 834 between the piston body 841 and the upper end 832 ofthe cylinder 830 and a lower chamber 835 between the piston body 841 andthe lower end 833 of the cylinder 830. The piston body is further formedwith a cavity 847 substantially bounded by the upper and lower pistonwalls 844, 845 and the annular piston wall 846 so as to preferably be inselective communication with both the upper and lower chambers 834, 835in cooperation with the upper and lower piston valves 842, 843, theoperation of which are explained more fully below. Connected to thepiston body 841 is a piston rod 870 having a hollow bore 873communicating between a drive end and a piston end, the drive end beingconnected to a drive mechanism such that the hollow bore 873 is incommunication with ambient air. The piston rod 870 passes through thecylinder 830 at its upper end 832, as through a gland (not shown), andthen through the upper chamber 834 so as to be connected at the oppositepiston end to the piston body 841. A lower piston valve 843 is installedon the piston body 841 so as to selectively seal the lower chamber 835from the cavity 847, while an upper piston valve 842 is installedadjacent to the piston body 841 so as to selectively seal the upperchamber 834 from the cavity 847. The construction and operation of theupper and lower piston valves are in many respects the same as thatdisclosed with respect to the exemplary embodiment shown in FIGS. 19-22.Specifically, here, the cavity 847 again comprises an upper piston bore848 formed in the upper piston wall 844 in communication with a lowerpiston bore 849 formed in the lower piston wall 845, with the piston rodessentially seated within the lower piston bore 849 while freelycommunicating with the upper piston bore 848 through one or morecross-holes 874 formed in the piston rod 870. In addition, an upperrelease valve 805 is installed within the piston body 841 offset fromthe cavity 847 so as to selectively communicate between the upperchamber 834 and the lower chamber 835. The upper release valve 805 hasan upwardly-projecting, spring-biased upper contact pin 807 configuredto contact the surface of the upper end 832 after the piston body 841has traveled sufficiently upwardly so as to effectively seal the upperexit bore 836, whereby displacement of the upper contact pin 807temporarily opens the upper release valve 805 and allows compressed airto pass from the upper chamber 834 through the upper release valve 805and into the lower chamber 835. Similarly, a lower release valve 806 isinstalled within the piston body 841 offset from the cavity 847 and fromthe upper release valve 805 so as to selectively communicate between thelower chamber 835 and the upper chamber 834, the lower release valve 806having a downwardly-projecting, spring-biased lower contact pin 808configured to contact the surface of the lower cylinder end 833 afterthe piston body 841 has traveled sufficiently downwardly so as to sealthe lower exit bore 837 and displace the lower contact pin 808 totemporarily open the lower release valve 806 and allow compressed air topass from the lower chamber 835 through the lower release valve 806 andinto the upper chamber 834.

In operation, then, referring now to FIGS. 24-27, the piston body 841 isslidably moved up and down within the cylinder 830 during operation ofthe air compression apparatus of the present invention as describedherein. In a first stage of operation as shown in FIG. 24, the pistonassembly 840 including the piston body 841 and piston rod 870 is movingdownwardly in the direction of arrows 801. As such, the inertial and airpressure effects cooperate to close the lower piston valve 843 bycausing the lower piston disk 867 to shift vertically upwardly intocontact with the o-ring 866, again, with or without the assistance of abiasing spring, thereby sealing off the hollow bore 873 from the lowerchamber 835. At the same time, the upper piston valve 842 is opened bythe inertial and air pressure effects cooperating to lift the collar 868to unseat the o-ring from the countersink formed about the upper pistonbore 848. Once the collar 868 has shifted upwardly as shown, inertialeffects caused by the rapidly descending piston 841 work to maintain thecollar's offset position with respect to the upper piston wall 844. Inthis stage, then, as shown by arrows 803, ambient air passing throughthe hollow bore 873 of the piston rod 870 passes through the cross-holes874, the opening or upper bore 848 of the cavity 847, and into the upperchamber 834. At the same time, because the lower piston valve 843 isclosed through the engagement of the lower piston disk 867 with theo-ring 866, further downward travel of the piston body 841 serves tocompress the air in the lower chamber 835. This process of introducingambient air into the upper chamber 834 and compressing the air in thelower chamber 835 continues until the piston body 841 nears the bottomend 833 of the cylinder 830 as again dictated by the structure andgeometry of the driving mechanism. Here, though, substantially at ornear the low point of the piston's downward travel in the direction ofarrows 801, as shown in FIG. 25, a second stage of operation occurswherein the lower end of the lower piston wall 845, configured in theexemplary embodiment as a downwardly-projecting boss, just enters thelower exit bore 837. Preferably, the outside diameter of the lowerpiston wall 845 is only slightly smaller than the inside diameter of thelower exit bore 837 so as to temporarily separate or seal off the exitbore from the lower piston chamber 835. Just at or after that time,further downward travel of the piston body 841 causes the lower releasevalve 806 to be actuated as the lower contact pin 808 contacts thesurface of the lower cylinder end 833. It will be appreciated that theexact location of the lower piston valve 843 relative to the lower end833 at this stage is not critical. The displacement of the lower contactpin 808 temporarily opens the lower release valve 806 and allowscompressed air to pass from the lower chamber 835 through the lowerrelease valve 806 and into the upper chamber 834, as indicated by arrows811. Those skilled in the art will appreciate that the gust ofcompressed air into the upper chamber 834 will cooperate with thereversal of direction of the piston assembly 840 as it starts upward toclose the upper piston valve 842 and hence begin the work of compressionin the upper chamber 834. Thus, once the piston body 841 has reached itslowest position within the cylinder 830, the air in the lower chamber835 has effectively reached its maximum pressure and is at that timeeither briefly introduced to the upper chamber 834 through the lowerrelease valve 806 or discharged from the lower chamber 835 as describedelsewhere herein. At that point, the piston 841 then transitions to athird stage of operation during which it is traveling upwardly withinthe cylinder 830 as indicated by arrows 802 in FIG. 26. During thisthird stage, it will again be appreciated that the inertial and airpressure effects cooperate to now close the upper piston valve 842 bycausing the collar 868 to shift downwardly as the piston body 841 ismoving rapidly upward, thereby seating the o-ring in the countersinkformed about the upper piston bore 848 to seal off the hollow bore 873from the upper chamber 834. At the same time, the lower piston valve 843is opened by the inertial and air pressure effects again cooperating topull the lower piston disk 847 downwardly and space it from the o-ring866. It will be appreciated that during this intermediate third stage ofupward travel of the piston 241, the upper and lower release valves 805and 806 remain closed. In this third stage, then, as shown by arrows804, ambient air passing through the hollow bore 873 of the piston rod870 passes out the end of the bore 873, through the lower bore 849 andbetween the lower piston disk 867 and the o-ring 866 into the lowerchamber 835. At the same time, because the upper piston valve 842 isclosed through the engagement of the o-ring 869 on the collar 868 withthe countersink of the upper bore 848, further upward travel of thepiston body 841 serves to compress the air in the upper chamber 834.This process of introducing ambient air into the lower chamber 835 andcompressing the air in the upper chamber 834 continues until the pistonbody 841 nears the top end 832 of the cylinder 830 as dictated by thestructure and geometry of the driving mechanism. Here, again,substantially at or near the high point of the piston's upward travel inthe direction of arrows 802, as shown in FIG. 27, a fourth stage ofoperation occurs wherein the upper piston valve 868, configured in theexemplary embodiment as an upwardly-projecting boss or collar, justenters the upper exit bore 836. Preferably, the outside diameter of thecollar 868 is only slightly smaller than the inside diameter of theupper exit bore 836 so as to temporarily separate or seal off the exitbore from the upper piston chamber 834. Just at or after that time,further upward travel of the piston body 841 causes the upper releasevalve 805 to be actuated as the upper contact pin 806 contacts thesurface of the upper cylinder end 832 after the piston body 841 hastraveled sufficiently upwardly, again, so as to receive the upper pistonvalve 842 within the upper exit bore 836. As such, the displacement ofthe upper contact pin 806 temporarily opens the upper release valve 805and allows compressed air to pass from the upper chamber 834 through theupper release valve 805 and into the lower chamber 835, as indicated byarrows 812. Those skilled in the art will appreciate that the gust ofcompressed air into the lower chamber 835 will cooperate with thereversal of direction of the piston assembly 840 as it starts downwardto again close the lower piston valve 843 and hence begin the work ofcompression in the lower chamber 835 during the first stage of operationdescribed above with respect to FIG. 24. Thus, once the piston body 841has reached its highest position within the cylinder 830, the air in theupper chamber 834 has effectively reached its maximum pressure and is atthat time either briefly introduced to the lower chamber 835 through theupper release valve 805 or discharged from the upper chamber 834 asdescribed. At that point, the piston 841 then transitions back to thefirst stage of operation during which it is traveling downwardly withinthe cylinder 830 as indicated by arrows 801 in FIG. 24. It will beappreciated, then, that the upper and lower release valves 805, 806 inthe alternative embodiment of FIGS. 22-27 cooperate with the inertialand other air flow and pressure effects during operation to selectivelyclose the respective lower and upper piston valves 843, 842 so as toenable compression of the air in the lower and upper chambers 835, 834.Based on the foregoing description of the cylinder 830 in operation, itwill be appreciated that the view shown in FIG. 23 with both the upperand lower piston valves 842, 843 open is essentially a static view ofthe construction for explanatory purposes and does not necessarilyreflect the positions of the moving parts of the assembly at any givenstage of operation.

Turning now to FIGS. 28-31, there is shown yet another exemplaryembodiment of the air compression apparatus of the present invention. Acylinder 930 has a piston assembly 940 inserted therein so as tosealably and slidably engage the inside surface of its annular wall 931.The piston assembly 940 is operably connected to a drive mechanism so asto move up and down within the cylinder as previously described.Specifically, the piston assembly 940 comprises a piston body 941 havingan upper piston wall 944 and an offset lower piston wall 945 joinedabout an annular piston wall 946. In this exemplary embodiment, theannular piston wall 946 is further formed with aradially-outwardly-projecting circumferential rib 965 so as to define anupper piston ring channel 960 and a lower piston ring channel 961. Whilethe respective upper and lower channels 960, 961 are shown as beingformed between the rib 965 and opposite radially outward flanges of theannular wall 946, it will be appreciated that the piston body 941 couldjust as easily be constructed as shown in FIGS. 19-27, wherein the upperand lower piston ring channels would effectively be formed between therib 965 and the upper and lower piston walls. In either construction, orsuch other construction as within the spirit and scope of the invention,an upper piston ring 962 is inserted within the upper piston ringchannel 960 and a lower piston ring 963 is inserted within the lowerpiston ring channel 961 so as to cooperate to sealably and slidablycontact the inside surface of the cylinder wall 931. Again, the upperand lower piston walls 944, 945 may be integral with the annular pistonwall 946 or may be installed thereon using any mechanical fasteningtechnique now known or later developed in the art. The piston body 941is further formed with a cavity 947 substantially bounded by the upperand lower piston walls 944, 945 and the annular piston wall 946.Accordingly, the cavity 947 comprises an annular space substantiallybetween the upper and lower piston walls 944, 945. One or more upperbreathing holes 948 are formed in the upper piston wall 944 so as toselectively communicate between the upper chamber 934 and the annularspace, and one or more lower breathing holes 949 are formed in the lowerpiston wall 945 so as to selectively communicate between the lowerchamber 935 and the annular space. While four round breathing holes areshown in the exemplary embodiment, it will be appreciated that thenumber, size, shape, and arrangement of the breathing holes may varywithout departing from the spirit and scope of the invention, which canbe said for the other embodiments of the present invention as well. Thepiston rod 970 is formed with cross-holes 974 and is connected to thepiston body 941 such that its hollow bore 973 communicates with theannular space through the cross-holes 974. An outwardly-opening lowerannular channel is formed in the lower piston wall 945 about each lowerbreathing hole 949 with a lower o-ring 966 seated therein. As such, inthe exemplary embodiment, the lower piston valve again comprises a lowervalve disk 967 movably mounted on the piston body 941 substantiallyadjacent to the lower piston wall 945 so as to selectively contact eachlower o-ring 966 and seal the lower breathing holes 949. Similarly, anoutwardly-opening upper annular channel is formed in the upper pistonwall 944 about each upper breathing hole 948 with an upper o-ring 969seated therein. Analogous to the lower piston valve, the upper pistonvalve comprises an upper valve disk 968 movably mounted on the pistonbody 941 substantially adjacent to the upper piston wall 944 so as toselectively contact each upper o-ring 969 and seal the upper breathingholes 948. In the exemplary embodiment of FIGS. 28-31, the piston end ofthe pivot rod 970 is closed, as with a plug, and formed with anoutwardly-opening threaded hole. A retainer having a threaded hole andan upwardly-facing shoulder is fastened to the bottom end of the pistonrod 970 substantially abutting the lower piston wall 945 through afastener screw. A similar retainer having a clearance hole for thepiston rod 970 and a downwardly-facing shoulder is installedsubstantially abutting the upper piston wall 944 and held in place by aretaining ring 909 or the like fixed on the piston rod 970. The upperand lower valve disks 968, 969 are thus retained adjacent to therespective upper and lower piston walls 944, 945 by the respectiveshoulders of the retainers while being free to shift vertically so as toselectively open and close the respective upper and lower piston valvesduring various stages of operation, as described more fully below.

Referring now to FIGS. 30 and 31, in operation, the piston body 941 isslidably moved up and down within the cylinder 930 during operation ofthe air compression apparatus of the present invention as describedherein. In a first stage of operation as shown in FIG. 30, the pistonbody 941 as driven through the piston rod 970 is moving downwardly inthe direction of arrows 901. As such, the inertial and air pressureeffects cooperate to close the lower piston valve by causing the lowerpiston disk 967 to shift vertically upwardly into contact with the lowero-rings 966, thereby sealing off the cavity 947 and, effectively, thehollow bore 973 from the lower chamber 935. At the same time, the upperpiston valve is opened by the inertial and air pressure effects againcooperating to lift the upper valve disk 968 out of contact with theupper o-rings 969. Once the upper valve disk 968 has shifted upwardly asshown, inertial effects caused by the rapidly descending piston 941 workto maintain the disk's offset position with respect to the upper pistonwall 944. It will be further appreciated that the retainer shown orother such structure serves to limit the movement of the upper valvedisk 968 relative to the piston body 941 and keep it substantiallyadjacent to the upper piston wall 944. In this stage, then, as shown byarrows 903, ambient air passing through the hollow bore 973 of thepiston rod 970 passes through the cross-holes 974, the breathing holes948 of the cavity 947, and into the upper chamber 934. At the same time,because the lower piston valve is closed through the engagement of thelower piston disk 967 with the o-rings 966, further downward travel ofthe piston body 941 serves to compress the air in the lower chamber 935.It will be appreciated that the more that pressure builds up in thelower chamber 935, the greater the seal between the lower piston disk967 and the o-rings 966 about the lower breathing holes 949, as theincreasing pressure applies greater and greater upward force against thelower piston disk 967. This process of introducing ambient air into theupper chamber 934 and compressing the air in the lower chamber 935continues until the piston body 941 reaches its lowest position withinthe cylinder 930, at which point the compressed air in the lower chamber935 is discharged as explained previously. At that point, the piston 941then transitions to a second stage of operation during which it istraveling upwardly within the cylinder 930 as indicated by arrows 902 inFIG. 31. During this stage, it will again be appreciated that theinertial and air pressure effects cooperate to now close the upperpiston valve by causing the upper valve disk 968 to shift downwardly asthe piston body 941 is moving rapidly upward, thereby sealing againstthe upper o-rings 966 about the upper breathing hole 948 to seal off thehollow bore 973 from the upper chamber 934. At the same time, the lowerpiston valve is opened by the inertial and air pressure effects againcooperating to pull the lower piston disk 947 downwardly and space itfrom the o-rings 966. It will be appreciated that the vacuum airpressure effect, specifically, is caused by the immediately precedingstage of operation during which high pressure compressed air wasevacuated from the lower chamber 935. Once the lower piston disk 967 hasshifted downwardly as shown, inertial effects caused by the rapidlyascending piston 941 work to maintain the disk's offset position withrespect to the lower piston wall 945 and the o-rings 966, specifically.It will be further appreciated that the structure of the lower pistonvalve shown as a retainer with a shoulder serves to retain the lowerpiston disk 967 substantially adjacent to the lower piston wall 945 andthat while such a retainer is shown, numerous other mechanical means,now known or later developed, for maintaining the position of the lowerpiston disk 967 relative to the lower piston wall 945 may be employed.In this second stage, then, as shown by arrows 904, ambient air pulledthrough the hollow bore 973 of the piston rod 970 passes through thecross-holes 974, the cavity 947, and the lower breathing holes 949 andthen between the lower piston disk 967 and the o-rings 966 into thelower chamber 935. At the same time, because the upper piston valve isclosed through the contact between the upper piston disk 968 and theupper o-rings 969, further upward travel of the piston body 941 servesto compress the air in the upper chamber 934. It will again beappreciated that the more that pressure builds up in the upper chamber934, the greater the seal about the upper breathing holes 969, as theincreasing pressure applies greater and greater downward force againstupper piston disk 968 as the piston 941 travels upward. This process ofintroducing ambient air into the lower chamber 935 and compressing theair in the upper chamber 934 continues until the piston body 941 reachesits highest position within the cylinder 930, at which point it willagain be appreciated that the air in the upper chamber 934 haseffectively reached its maximum pressure and is at that time discharged.At that point, the piston 941 then transitions back to the first stageof operation during which it is traveling downwardly within the cylinder930 as indicated in FIG. 30.

Turning to FIGS. 32-35, there is shown yet another exemplary embodimentof the air compression apparatus of the present invention involving aconstruction analogous to that of the previous embodiment of FIG. 28-31,with a few notable changes. Specifically, the piston assembly 1040 againcomprises a piston body 1041 having an upper piston wall 1044 and anoffset lower piston wall 1045 joined about an annular piston wall 1046.Once more, at least two of these elements may be of a unitaryconstruction, and any of them may be joined together using any means nowknown or later developed in the art. In this exemplary embodiment, theannular piston wall 1046 is further formed with aradially-outwardly-opening circumferential groove 1065 in which a pistono-ring 1066 is seated. The piston ring 1062 is then seated in the pistonchannel 1060 formed circumferentially about the annular piston wall 1046between the radially outward edges of the upper and lower piston walls1044, 1045 so as to cooperate with the piston o-ring 1066 to sealablyand slidably contact the inside surface of the cylinder wall 1031. Apath for the ambient air being pulled through the hollow bore 1073 ofthe piston rod 1070 is formed generally as previously. Regarding thelower piston valve, however, in this exemplary embodiment, the lowervalve disk 1067 is formed with two concentric upwardly-opening first andsecond annular channels 1005, the channels being configured to define aseal area therebetween that is substantially adjacent to the lowerbreathing holes 1049. A first lower o-ring 1011 is seated within thefirst annular channel 1005 and a second lower o-ring 1012 is seatedwithin the second annular channel 1006, the o-rings selectivelycontacting the lower piston wall 1045 so as to seal the lower breathingholes 1049. Again, an end wall plug 1013 is installed within the hollowbore 1073 substantially at the end of the piston rod 1070 and formedwith an outwardly-opening threaded hole configured to threadably receivea fastener 1007. A sleeve is installed over the fastener 1007 to givethe fastener something to tighten against so as to form a rigidconnection of the lower piston wall 1045 to the piston rod 1070. Thelower valve disk is further formed with a clearance hole 1014 offsetfrom and substantially concentric with the first and second annularchannels 1005, 1006 such that the fastening screw 1007 and sleeve passthrough the clearance hole 1014. A similar clearance hole or a threadedhole is formed in the lower piston wall 1045 so as to allow the screw tobe secured within the plug 1013. Furthermore, a return spring 1008 maybe positioned about the sleeve and threaded body of the screw 1007between its head and the lower piston disk 1067 so as to bias the diskupwardly.

Referring now to FIGS. 34 and 35, in operation, the piston body 1041 isslidably moved up and down within the cylinder 1030 during operation ofthe air compression apparatus of the present invention as describedherein. Once more, in a first stage of operation as shown in FIG. 34,the piston body 1041 as driven through the piston rod 1070 is movingdownwardly in the direction of arrows 1001. As such, the inertial andair pressure effects cooperate to close the lower piston valve bycausing the lower piston disk 1067 to shift vertically upwardly so as tobring the first and second lower o-ring 1011, 1012 into contact with thelower piston wall 1045, thereby sealing the lower breathing holes 1049and, effectively, the hollow bore 1073 from the lower chamber 1035. Itwill be further appreciated that the structure of the lower piston valveshown as including a fastener 1007 configured with return spring 1008serves to further lift and bias the lower valve disk 1067 upwardly. Atthe same time, the upper piston valve is as before. In this stage, then,as shown by arrows 1003, ambient air passing through the hollow bore1073 of the piston rod 1070 passes into the upper chamber 1034. At thesame time, because the lower piston valve is closed, further downwardtravel of the piston body 1041 serves to compress the air in the lowerchamber 1035. This process of introducing ambient air into the upperchamber 1034 and compressing the air in the lower chamber 1035 continuesuntil the piston body 1041 reaches its lowest position within thecylinder 1030, at which point the compressed air in the lower chamber1035 is discharged. At that point, the piston 1041 then transitions to asecond stage of operation during which it is traveling upwardly withinthe cylinder 1030 as indicated by arrows 1002 in FIG. 35. During thisstage, the upper piston valve is again closed as in previousembodiments, while the lower piston valve is opened by the inertial andair pressure effects again cooperating to pull the lower piston disk1067 downwardly, even against the relatively light force of the returnspring 1008, so as to space the o-rings 1011, 1012 from the lower pistonwall 1045 and allow air to flow through the lower breathing holes 1049.It will be appreciated that the vacuum air pressure effect,specifically, is caused by the immediately preceding stage of operationduring which relatively high pressure compressed air was evacuated fromthe lower chamber 1035, which cooperates with inertia to help shift thelower valve disk 1067 downwardly against the resistance of the returnspring 1008. Again, though such a fastening and biasing structure isshown, it will be appreciated that numerous other mechanical means, nowknown or later developed, for maintaining the position of the lowerpiston disk 1067 relative to the lower piston wall 1045 may be employed.In this second stage, then, as shown by arrows 1004, ambient air pulledthrough the hollow bore 1073 of the piston rod 1070 passes through thelower breathing holes 1049 and then between the lower piston wall 1045and the lower piston disk 1067 and its o-rings 1011, 1012 into the lowerchamber 1035. At the same time, because the upper piston valve isclosed, further upward travel of the piston body 1041 serves to compressthe air in the upper chamber 1034. This process of introducing ambientair into the lower chamber 1035 and compressing the air in the upperchamber 1034 continues until the piston body 1041 reaches its highestposition within the cylinder 1030, at which point it will again beappreciated that the air in the upper chamber 1034 has effectivelyreached its maximum pressure and is at that time discharged. At thatpoint, the piston 1041 then transitions back to the first stage ofoperation during which it is traveling downwardly within the cylinder1030 as indicated in FIG. 34.

Turning now to FIGS. 36 and 37, there is shown yet another exemplaryembodiment of the air compression apparatus of the present inventioninvolving a construction analogous to that of the previous embodiment ofFIG. 28-31, with a few more notable changes. Specifically, the pistonassembly 1140 again comprises a piston body 1141 of either unitary ormodular construction having an upper piston wall 1144 and an offsetlower piston wall 1145 joined about an annular piston wall 1146. In thisexemplary embodiment, the annular piston wall 1146 is again formed witha radially-outwardly-opening circumferential groove in which a pistono-ring is seated. Here, the piston ring 1162 is formed with one or moreradially-outwardly-opening circumferential piston ring grooves 1163. Inoperation, as the piston ring 1162 slidingly and sealingly engages theinside surface of the cylinder wall 1131, the one or more grooves 1163serve to lessen the overall frictional drag against the cylinder wall1131 by reducing the overall contact area while effectively setting upimproved sealing dynamics. That is, each of the circumferential peaksadjacent to the respective grooves 1163 is effectively a separate pistonring, whereby air attempting to pass by the entire piston ring 1162 mustessentially overcome each such sub-piston ring. It will be appreciatedthat air doing so will then effectively gather in the groove beyond thecompromised sub-piston ring before then “attempting” to breach the nextsub-piston ring. Put another way, individual seal areas on the pistonring 1162 number one more than the number of grooves 1163. For example,in the exemplary embodiment shown, four offset circumferential pistongrooves 1163 are formed in the piston ring 1162, so that effectivelyfive peaks, or seals, must be passed to compromise the piston ring andallow unwanted air to move between chambers on opposite sides of thepiston 1141. It will be further appreciated that the radially-outwardforce applied to the back of the piston ring 1162 by the piston o-ring1166 further improves the sealing performance. As a further improvementto the piston ring 1162, a diagonal slit 1164 is formed in the pistonring 1162 rather than the conventional vertical slit. In this way, aspressure is applied to the piston ring 1162 from either direction as thepiston 1141 is moving up or down in the cylinder 1130 and compressingair in the upper or lower chambers, the outward pressure on the pistonring 1141 as air attempts to get under and by it, though effectivelyslightly increasing the circumference of the piston ring, which canresult, under normal circumstances, in slightly opening the verticalslit and allowing air to leak through, here only shifts one side of thediagonal slit 1164 with respect to the other while still keeping bothsides of the slit in contact and not allowing any air to pass. Tofurther facilitate this effect, the width of the piston ring 1162 in thevicinity of the slit 1164 can be slightly reduced to allow for thisshifting along the slit to happen within the fixed piston channel. Inorder to accommodate the grooved piston ring 1162 of the presentembodiment, it will be appreciated by those skilled in the art that theoutside diameter of the annular piston wall 1146 may be reduced so as toeffectively form a deeper piston ring channel. As best shown in FIG. 37,a further modification to the structure of the air compression apparatusof the present invention shown in the exemplary embodiment is also madewith respect to the structure of the annular piston wall 1146. Multipleradially-inwardly-projecting longitudinal fins 1109 are formed about theinside surface of the annular piston wall 1146. It will be appreciatedby those skilled in the art that such fins 1109 serve to reduce noiselevels during operation of the air compression apparatus by effectivelynot allowing sound waves to bounce directly off the inside surface ofthe annular piston wall 1146 and back up the hollow piston rod 1170.This effect, combined with the other improvements in the noise level ofoperation achieved, in part, as explained above, through the relativelyslower speeds of operation and the relatively gentle “squeezing,” ratherthan “slamming,” of the air within the cylinder, serves to furtherimprove the quietness of the air compression apparatus of the presentinvention. It is noted that even the direction of air movement asessentially always being into the hollow piston rod, particularly in thedouble-acting embodiments of the cylinder, and the length over whichthis happens further opposes the travel of shock or sound waves out ofthe piston rod during operation of the compressor. Moreover, thoseskilled in the art will appreciate that, as explained above withreference to the exemplary embodiment shown in FIGS. 16 and 17, theinclusion of a woven or mesh sleeve or other such acoustic sleeve orstrip within the hollow piston rod serves to still further reduce theoperational noise level of the air compression apparatus of the presentinvention.

Referring now to FIGS. 38-48, generally, the air compression apparatusof the present invention may have a cylinder formed at one or both endswith a breathing chamber, or a sub-chamber in which compressed air maybe collected from the main upper or lower chamber in which the work ofcompression by the piston is accomplished in order to allow for moreefficient transfer of the compressed air out of the cylinder and into apressure tank. That is, it will be appreciated that the Bernoulli effectexperienced when pushing compressed, or high pressure, air through arestriction, namely, the exit valve, can have a detrimental effect onthe efficiency and quietness of a compressor's operation. As such, it isadvantageous to effectively stage the compressed air in a sub-chamber,or breathing chamber, between the upper and lower chambers of thecylinder and the respective upper and lower exit ports. The principlesof the present invention have thus been further applied to this problemto achieve yet another improvement to the overall operation of an aircompression system. Accordingly, while the following exemplaryembodiments show various means by which a breathing chamber can beconstructed so that compressed air can selectively pass into thebreathing chamber before going through the exit valve and through an airline to the tank, those skilled in the art will appreciate that numerousother constructions are possible without departing from the spirit andscope of the invention. Moreover, with respect to the very exemplaryembodiments shown, it will be further appreciated that the sizes andproportions of the various components are also exemplary and may bevaried to suit particular applications.

Turning first to FIGS. 38-40, an upper end 1232 of the cylinder 1230 isformed by an upper cylinder wall 1290 and an offset upper chamber plate1291 sealably installed within the cylinder so as to form therebetweenan upper breathing chamber 1292. The upper chamber plate 1291 is formedwith at least one selectively sealable upper breathing hole 1293communicating between the upper chamber 1234 and the upper breathingchamber 1292. The upper chamber plate 1291 is further formed with anupwardly-extending boss that can itself accommodate the piston rod 1270or have a further tube installed therein. Either way, substantiallyaxially aligned piston bores are formed in the upper cylinder wall 1290and the upper chamber plate 1291 for the passage therethrough of thepiston rod 1270, whereby any such construction effectively serves as agland through which the piston rod 1270 slidably operates. Aspreviously, various combinations of such components may be unitary ormodular in construction using techniques now known or later developed inthe art. In the exemplary embodiment, an o-ring is seated on the upperend of the upwardly-extending boss formed on the upper chamber plate1291 such that the upper cylinder wall 1290 sealably sits thereon, theassembly then being held in such arrangement within the cylinder wall1231 by opposing retaining rings or other such structure now known orlater developed. An upwardly-opening upper annular channel 1294 isformed in the upper chamber plate 1291 about each upper breathing hole1293 with an upper o-ring 1295 seated therein, as best shown in FIG. 39.An upper chamber disk 1296 is movably mounted within the upper breathingchamber 1292 substantially adjacent to the upper chamber plate 1291 soas to selectively contact the upper o-rings 1295 and seal the upperbreathing holes 1293. Again, while four round breathing holes are shownin the exemplary embodiment, it will be appreciated that the number,size, shape, and arrangement of the breathing holes may vary withoutdeparting from the spirit and scope of the invention. Theupwardly-projecting boss may be formed with a flange or have a retainingring or the like installed thereon so as to limit the verticaldisplacement of the upper chamber disk 1296 during operation. It will beappreciated by those skilled in the art that with this basicconstruction, air will move from the upper chamber 1234 to the upperbreathing chamber 1292 based on principles of fluid dynamics, wherebythe air in the system will tend to move from areas of high pressure toareas of low pressure wherever possible. Accordingly, it will be furtherappreciated that where a standard connector 1280 is installed in theupper cylinder wall 1290 as shown or in the cylinder wall 1231 betweenthe upper cylinder wall 1290 and the upper chamber plate 1291, thepressure in the breathing chamber will at least tend toward the pressurein the line and, thus, the pressure in the tank, assuming that there isno check valve in the air line either. In this scenario, air compressedin the upper chamber 1234 will only be able to unseat the upper valvedisk 1296 and move into the breathing chamber 1292 as shown by arrows1201 in FIG. 40, when its pressure is greater than that of the tank.Otherwise, if the tank pressure is greater, no more air can enter thebreathing chamber or the tank itself. It will be appreciated that wherethe tank pressure is greater, this pressure effectively acts downwardlyon the upper chamber disk 1296 so as to force it into contact with theupper o-rings 1295, as shown in FIG. 38, effectively sealing off thebreathing chamber 1292 from the upper chamber 1234 until the pressurewithin the tank drops or the pressure within the upper chamberincreases.

Turning to FIGS. 41-43, there is shown an alternative embodiment upperbreathing chamber in connection with the air compression apparatus ofthe present invention. The upper end 1332 of the cylinder 1330 is againformed by an upper cylinder wall 1390 and an offset upper chamber plate1391 sealably installed within the cylinder so as to form therebetweenan upper breathing chamber 1392. The upper chamber plate 1391 is formedwith at least one selectively sealable upper breathing hole 1393communicating between the upper chamber 1334 and the upper breathingchamber 1392. The upper chamber plate 1391 is further formed with anupwardly-extending boss that can itself accommodate the piston rod 1370or have a further tube installed therein. Either way, substantiallyaxially aligned piston bores are formed in the upper cylinder wall 1390and the upper chamber plate 1391 for the passage therethrough of thepiston rod 1370, whereby any such construction effectively serves as agland through which the piston rod 1370 slidably operates. Aspreviously, various combinations of such components may be unitary ormodular in construction using techniques now known or later developed inthe art. An o-ring is again seated on the upper end of theupwardly-extending boss formed on the upper chamber plate 1391 such thatthe upper cylinder wall 1390 sealably sits thereon, the assembly thenbeing held in such arrangement within the cylinder wall 1331 by opposingretaining rings or other such structure now known or later developed. Anupwardly-opening counterbore 1394 is formed in the upper chamber plate1391 about each upper breathing hole 1393 with an upper o-ring 1395seated therein, as best shown in FIG. 42. Also shown, anupwardly-opening circumferential channel 1397 is formed in the upperchamber plate so as to substantially connect the counterbores 1394, ofwhich there are four in the exemplary embodiment. As explained morefully below, the channel further enables air flow through the breathingholes 1393. A ball 1396 is movably seated within each of thecounterbores 1394 so as to selectively seal the breathing holes 1393through contact with the respective o-rings 1395. In an alternativeembodiment, a gasket material is seated or pinched substantially at thebase of each counterbore 1394. It will be appreciated by those skilledin the art that with this basic alternative construction, air will movefrom the upper chamber 1334 to the upper breathing chamber 1392 againbased on pressure differential. Accordingly, where no one-way valves areemployed in the air lines, the pressure in the breathing chamber 1392will tend toward the pressure in the tank. In this scenario, aircompressed in the upper chamber 1334 will only be able to unseat theballs 1396 and move into the breathing chamber 1392 as shown by arrows1301 in FIG. 41, when its pressure is greater than that of the tank. Itwill be appreciated that the balls 1396 will likely never be positionedspaced from the counterbores 1394 as shown, such that the balls in thislocation are merely exemplary and to facilitate viewing of the otherfeatures of the apparatus. It is further contemplated that a retainingdisk or the like may be installed on the upper chamber plate 1391, as ina notch on its boss, so as to effectively limit the verticaldisplacement of the balls in much the same way that a retaining ring orthe like may limit the movement of the upper chamber disk 1296. In anyevent, when the pressure in the upper chamber 1334 is greater than thatof the breathing chamber, and thus, the tank, the balls 1396 will beunseated from the o-rings 1395 sufficiently to allow air to move fromthe upper chamber 1334 through the breathing holes 1393 and thecounterbores 1394 and around the balls 1396 into the breathing chamber1392. Again, the circumferential channel 1397 further enables thisbreathing. Otherwise, if the tank pressure is greater, no more air canenter the breathing chamber or the tank itself. It will be appreciatedthat where the tank pressure is greater, this pressure effectively actsdownwardly on the balls 1396 so as to force them into their respectivecounterbores 1394 and, thus, contact with the upper o-rings 1395, asshown in FIG. 43, effectively sealing off the breathing chamber 1392from the upper chamber 1334 until the pressure within the tank drops orthe pressure within the upper chamber increases.

Turning now to FIGS. 44-46, a further exemplary embodiment of the aircompression apparatus is shown directed to a lower breathing chamberconfiguration. A lower cylinder wall 1490 is sealably installed withinthe annular cylinder wall 1431 as by a screw fastener, though anyassembly means now know or later developed may be employed. The lowercylinder wall 1490 is formed with an upwardly-projecting sidewall thatextends into the cylinder and is configured to sealingly retain a lowerchamber plate 1491 offset from the substantially horizontal base of thelower cylinder wall 1490 so as to form therebetween a lower breathingchamber 1492. The lower chamber plate 1491 is formed with at least oneselectively sealable lower breathing hole 1493 communicating between thelower chamber 1435 and the lower breathing chamber 1492. A lower chamberdisk 1496 is movably mounted within the lower breathing chamber 1492substantially adjacent to the lower chamber plate 1491. As best shown inFIG. 45, the lower chamber disk 1496 is formed with an upwardly-openinglower annular channel 1494 having a lower o-ring 1495 seated therein.The lower chamber disk 1496 may be further formed with at least onelower chamber passage 1497 radially-outwardly offset from the lowerannular channel 1494. While the passage 1497 is configured in theexemplary embodiment as an arrangement of holes, it will be appreciatedthat virtually any opening configuration that will allow air to flowthrough the lower breathing hole 1493 and around the lower chamber disk1496 when it is shifted downwardly so as to space the o-ring 1495 fromthe lower chamber plate 1491 can be employed. It will be furtherappreciated that only a minimal amount of structure radially outward ofthe annular channel 1494 is required, primarily to stabilize the lowerchamber disk 1496 laterally within the lower breathing chamber. As such,for example, spaced apart spines projecting radially outwardly from justbeyond the annular channel 1494 could also be employed. A return spring1408 is positioned substantially between the lower chamber disk 1496 andthe lower cylinder wall 1490 so as to bias the lower chamber diskupwardly. In use, as with the upper breathing chamber exemplaryembodiments shown and described, the pressure in the lower breathingchamber will at least tend toward the pressure in the line and, thus,the pressure in the tank, assuming that there is no check valve in theair line. A two-way, sealed connector 1480 is shown as connecting theair line 1482 to the lower cylinder wall 1490, though it will beappreciated that any such connector now known or later developed in theart may be employed. Air compressed in the lower chamber 1435 will onlybe able to unseat the lower valve disk 1496 and move into the lowerbreathing chamber 1492 as shown by arrows 1401 in FIG. 46 when itspressure is greater than that of the tank. In addition, the pressure inthe lower chamber 1435 must also be able to overcome the force of thereturn spring 1408 biasing the lower valve disk 1496 upwardly.Otherwise, if the tank pressure is essentially greater, no more air canenter the lower breathing chamber or the tank itself. It will beappreciated that where the tank pressure is greater, this pressureeffectively acts upwardly on the lower chamber disk 1496 so as to forceits o-ring 1495 into contact with the lower chamber plate 1491, as shownin FIG. 44, effectively sealing off the lower breathing chamber 1492from the lower chamber 1435 until the pressure within the tank drops orthe pressure within the lower chamber increases.

Referring to FIGS. 47 and 48, yet another alternative embodiment of thelower end 1532 of an air compression apparatus is shown as having anannular body configured with a circumferential o-ring for receipt withinan annular cylinder wall as generally described above. The annular lowerend 1532 includes a lower breathing chamber 1592 defined by theintersection of a substantially vertical, upwardly-opening counterbore1593, formed in what is essentially the lower chamber plate, and asubstantially horizontal cross-hole 1594 configured for receipt of aconnector (not shown). An upwardly-projecting support post 1595 isformed on what is essentially the lower cylinder wall so as to extendinto the lower breathing chamber 1592 substantially coaxially with thecounterbore 1593. Though the lower end 1532 is shown as being formed ofa unitary construction, it will be appreciated by those skilled in theart that it could also be modular and include such components as a lowercylinder wall, from which the support post extends, a lower chamberplate, either of which having a vertical annular wall configured tosealingly engage the other, whereby the size of the lower breathingchamber of the exemplary embodiment could be increased. A plug 1597 isthreadably or otherwise installed in the counterbore 1593 having adownwardly-facing seat intersected by a breathing hole 1598. A ball 1596is movably inserted within the counterbore 1593 so as to selectivelyseal the at least one lower breathing hole 1598 and is biased upwardlyby a return spring 1508 positioned about the support post 1595. Thus,again, assuming that the pressure in the lower breathing chamber 1592 atany given time is roughly equivalent to the tank pressure, it will beappreciated that the ball 1596 will not be displaced so as to allow airto flow into the lower breathing chamber until the pressure in the lowerchamber is greater than the tank pressure. When the tank pressure isgreater, it cooperates with the return spring 1508 to bias the ball 1596upwardly in sealing engagement with the plug 1597. It will beappreciated by those skilled in the art that the embodiments of theupper and lower breathing chambers so shown and described are merelyexemplary and that numerous other configurations are possible withoutdeparting from the spirit and scope of the invention.

Referring now to FIGS. 49-51, there is shown a still further exemplaryembodiment of the air compression apparatus 1600 of the presentinvention essentially incorporating the principles of construction anduse discussed above in a multi-cylinder arrangement. A tank 1602 isinstalled on a frame 1606 along with a motor 1604. The motor isconfigured with a driving shaft 1608 and pulley 1612 arranged to turn aflywheel 1620 through a belt 1614 as above. Though a belt tensionerapparatus could again be provided to take up any slack in the belt 1614during operation, it is not necessary because the flywheel is circular.Alternatively, the motor could be pivotally or dynamically mounted tothe frame so as to allow some relative movement between the drive pulleyand the flywheel to take care of any variance in tension. A flywheelcrankpin 1622 is installed on the flywheel in a first position andpivotally connected to a flywheel intake block rigidly mounted to afirst piston rod 1670 being driven within a first cylinder 1630 that ispivotally mounted at its base to the frame 1606 through a first pivotpin 1658. First and second pillow block bearings 1603, 1604 areinstalled on the tank in an offset arrangement such that respectivefirst and second through holes formed in the bearings 1603, 1604 aresubstantially aligned. A flywheel shaft 1625 rigidly mounted within theflywheel 1620 then rotatably passes through both block bearings 1603,1604 so as to extend beyond the opposite side of the tank 1602. A drivearm 1605 is rigidly mounted to the flywheel shaft 1625 opposite theflywheel 1620. The drive arm 1605 has a drive arm crankpin 1623installed thereon and is mounted on the flywheel shaft 1625 such thatthe drive arm crankpin 1623 is out of phase with the flywheel crankpin1622, as explained more fully below. A drive arm intake block 1627 ispivotally mounted on the drive arm crankpin 1623 which is then rigidlyinstalled on a second piston rod 1671 of a second cylinder 1631pivotally mounted on a second pivot pin 1659 installed on the frame1606. The first and second cylinders 1630, 1631 are, thus, pivotallyinstalled on the frame 1606 in a substantially offset arrangement aboutthe tank 1602. The first cylinder has a first piston body sealingly andslidably installed therein so as to form a first upper chamber above thefirst piston body and a first lower chamber below the first piston body,the first piston body being further formed with a first cavity incommunication with the first lower chamber. Likewise, the secondcylinder has a second piston body sealingly and slidably installedtherein so as to form a second upper chamber above the second pistonbody and a second lower chamber below the second piston body, the secondpiston body being further formed with a second cavity in communicationwith the second lower chamber. A first piston rod 1670 is rigidlyconnected to the flywheel intake block 1626 and a second piston rod 1671is rigidly connected to the drive arm intake block 1627, each having ahollow bore configured to communicate with the ambient air through therespective intake block. As in the other exemplary embodiments, thepiston rods pass through the cylinders and the upper chambers so as tobe connected to the respective pistons operating within the cylinders1630, 1631. Furthermore, at least lower piston valves are installed onthe respective piston bodies so as to selectively seal the first lowerchamber from the first cavity and the second lower chamber from thesecond cavity. In the exemplary embodiment, air lines (not shown) againconnect the one or more outlets at least of the lower chambers of eachcylinder to the tank, though it will be appreciated that the cylinderscan each be connected to further cylinders or holding tanks in seriesfor further compression. As such, in operation, rotation of the flywheel1620 as driven by the motor 1604 acts on the first piston rod 1670through the flywheel crankpin 1622 and the flywheel intake block 1626 tocause the first piston body to travel within the first cylinder 1630,alternately opening the first lower piston valve to pull ambient airthrough the hollow piston rod into the first lower chamber and closingthe first lower piston valve to compress the air in the first lowerchamber. At the same time, rotation of the flywheel 1620 acts on thesecond piston rod 1671 through rotation of the flywheel shaft 1625translating to rotation of the drive arm 1605 and radial movement of thedrive arm crankpin 1623 and the drive arm intake block 1627 to cause thesecond piston body to travel within the second cylinder 1631,alternately opening the second lower piston valve to pull ambient airthrough the second hollow piston rod 1671 into the second lower chamberand closing the second lower piston valve to compress the air in thesecond lower chamber. Preferably, the opening of the first lower pistonvalve is not concurrent with the opening of the second lower pistonvalve, and the closing of the first lower piston valve is not concurrentwith the closing of the second lower piston valve. This is accomplisheddue to the flywheel crankpin 1622 and the drive arm crankpin 1623 beingout of phase, as best seen in FIGS. 50 and 51. As a result, it will beappreciated by those skilled in the art that the higher torque output ofthe motor, as when a piston is nearing the top or bottom of its traveland essentially maximum compression is being done in the cylinder, isnot demanded of both cylinders at the same time. Rather, when onecylinder is requiring more power, it is desirable that the other isdoing the relatively easier work of gathering air. In an exemplaryembodiment, the respective crankpins, and thus cylinders, may beapproximately sixty or one hundred twenty degrees out of phase, thoughit will be further appreciated that numerous such arrangements may beoptimal depending on the cylinder arrangement and application. It willbe appreciated that cylinders of different size and stroke length can beemployed in the same compressor, as when staging of the compression isto be accomplished, for example, which would further effect thekinematic arrangement. Moreover, other changes, such as the addition ofa counterweight to the drive arm 1605 substantially opposite the drivearm crank pin 1623, may be made to take further advantage of theinertial characteristics of the air compression apparatus of the presentinvention.

With all of the embodiments of the air compression apparatus of thepresent invention, o-rings and the like may be used liberally throughoutthe construction to provide seals between all mechanically joinedcomponents. An example of the kind of o-ring employed in the presentinvention is a Viton® o-ring having a temperature range of −10 to 400degrees Fahrenheit (−23 to 204 degrees Celsius). Furthermore, it is tobe understood that all o-rings are to be seated as by being mechanicallytrapped or press fit or otherwise secured so as to effectively remain inthe positions shown, as by means now known or later developed in theart. This is to be particularly understood for those o-rings seatedaround breathing holes in many of the exemplary embodiments, such thateven as sealing members are selectively shifted out of contact with theo-rings, they remain seated in their respective channels. The othercomponents shown and described, except as otherwise mentioned, areprimarily constructed of aluminum or steel. The gland sealing the pistonrod is generally formed as is known in the art of bronze, though it willbe appreciated that in the present invention the bushing is capable ofbeing relatively longer due to the substantially coaxial travel of thepiston assembly within the cylinder as described above. This increasedlength of the gland's bronze bushing results in, among other things,better mechanical support and sealing about the piston rod as well asrelatively longer life. Moreover, it will be appreciated by thoseskilled in the art that numerous combinations of the structure andgeometry of the drive mechanism and the cylinder arrangements shown anddescribed can be practiced depending on the application and performancerequirements. Drives and cylinders can be mixed and matched to suitparticular needs, such that the embodiments shown are to be understoodas merely exemplary. Particularly, the lengths and diameters of thecylinders and piston assemblies can vary widely from the geometriesshown and described without departing from the spirit and scope of theinvention. Specifically, while the hollow piston rod is shown anddescribed herein as being tubular or annular, it will be appreciatedthat the rod can take a variety of configurations without departing fromthe invention. Again, the cylinders themselves can be arranged inparallel or in series, and the described advantages can be achievedusing the disclosed drive mechanisms with virtually any cylinderarrangement now known or later developed, and need not be the novelcylinder design of the present invention whereby ambient air isintroduced into the cylinder through the hollow piston rod. Or,advantages in construction and use can be achieved through the novelcylinder design of the present invention involving breathing through thehollow piston rod alone, again, whether the cylinder is single-acting ordouble-acting, single-staging or multi-staging, or actuated by a drivemechanism alone or along with other cylinders, and so need not involveany of the particular drive mechanisms disclosed to still derive theadvantages of the cylinder construction described herein. Thus, whileuse of both the disclosed drive mechanisms and cylinders is preferable,it is not required and the invention is not so limited.

Accordingly, it will be appreciated by those skilled in the art that thepresent invention is not limited to any particular configuration of thecompressor and its cylinder or cylinders, and that numerous suchconfigurations are possible without departing from the spirit and scopeof the invention. Therefore, aspects of the present invention may bemore generally described as improved air compression providing for arelatively longer or larger-volume working stroke of each pistoncombined with a coordinated variance in the speed of the piston duringits stroke to produce smoother and more efficient compression. Theimproved compressor may further consist, in part, of one or more pistonsthat compress the air both on the “upward” and “downward” strokes. Inany such embodiments, a hollow rod is preferably attached to the pistonand passed through a gland at the top end of the cylinder so as toprovide a compressible space above the piston between the hollow rod andthe wall of the cylinder, i.e., the upper chamber, and between thepiston and the bottom of the cylinder, i.e., the lower chamber, suchthat the piston compresses air both on the “upstroke” and on the “downstroke.” In many of the exemplary embodiments, the cylinder is ofextended length and the system operates at a relatively low number ofstrokes per minute so that a greater volume of air is compressed to ahigher pressure with less physical motion of the parts and, thus, withincreased potential for heat dissipation between strokes. Moreover, theimproved breathing of the cylinder through the piston assembly throughphysically separating the chamber inlet and outlet locations, or placingthe inlets and outlets on different surfaces, yields greatly improvedair flow through the cylinder, which provides numerous advantages asdescribed herein. Accordingly, the extended length or larger volume ofthe cylinder and the reduced and variable rate of motion of the pistonwithin the cylinder of the typical embodiment of the compressor of thepresent invention along with the introduction of ambient air into thecylinder through a hollow piston rod provide for smooth compression andfor less demand of power with a larger volume of compressed air perstroke, ultimately resulting in the compressor of the present inventionoperating more efficiently. Such other structure and resulting benefitsof operation are possible without departing from the spirit and scope ofthe invention.

While aspects of the invention have been described with reference to atleast one exemplary embodiment, it is to be clearly understood by thoseskilled in the art that the invention is not limited thereto. Rather,the scope of the invention is to be interpreted only in conjunction withthe appended claims and it is made clear, here, that the inventorbelieves that the claimed subject matter is the invention.

1. An air compression apparatus having a frame and a tank and a motor mounted to the frame, the improvement comprising: a drive mechanism operably connected to the motor; at least one piston assembly operably connected to the drive mechanism and configured to move within a respective cylinder mounted to the frame, the piston assembly comprising: a piston body sealingly and slidably installed within the cylinder so as to form an upper chamber above the piston body and a lower chamber below the piston body, the piston body being further formed with a cavity in communication with at least the lower chamber; a piston rod having a hollow bore communicating between a drive end and a piston end, the drive end being connected to the drive mechanism such that the hollow bore is in communication with ambient air, the piston rod passing through the cylinder and the upper chamber so as to be connected at the opposite piston end to the piston body, the piston rod having at least one opening formed therein substantially at the piston end such that the hollow bore is in communication with the cavity; and a lower piston valve installed on the piston body so as to selectively seal the lower chamber from the cavity; and at least one air line connected between the cylinder and the tank for the passage of compressed air therethrough, whereby upward travel of the piston body as caused by the drive mechanism acting through the piston rod opens the lower piston valve and allows ambient air to be drawn through the hollow bore, the at least one opening, and the cavity into the lower chamber, and whereby downward travel of the piston body as caused by the drive mechanism acting through the piston rod closes the lower piston valve so as to compress the air within the lower chamber.
 2. The apparatus of claim 1, wherein: the cylinder is pivotally mounted on a pivot pin; and the drive mechanism comprises: a flywheel rotatably mounted to the frame; a drive pulley installed on a drive shaft of the motor so as to be substantially coplanar with the flywheel; a drive belt engaging the drive pulley and the flywheel so that torque from the motor is transmitted to the flywheel through the drive belt; a crankpin mounted on the flywheel; and an intake block pivotally mounted on the crankpin so as to connect the piston rod to the flywheel, the intake block being formed with at least one passage for the communication of ambient air through the passage and into the hollow bore, whereby rotational movement of the flywheel translates into oscillating movement of the cylinder about the pivot pin and simultaneous axial displacement of the piston body within the cylinder.
 3. The apparatus of claim 2, wherein: a pivot arm is pivotally mounted to the frame on a pivot shaft; the cylinder is mounted to the pivot arm on the pivot pin offset from the pivot shaft; and the drive mechanism further comprises a guide bar mounted to the pivot arm at a lower end, the guide bar having a slot formed at an opposite upper end such that the crankpin passes into the slot, whereby movement of the crankpin with rotation of the flywheel causes oscillating movement of the guide bar about the pivot shaft, translating into vertical and horizontal oscillating movement of the cylinder.
 4. The apparatus of claim 3, wherein the slot is substantially linear.
 5. The apparatus of claim 3, wherein the slot is substantially S-shaped.
 6. The apparatus of claim 2, wherein: the flywheel is formed with an outer rim defining an elliptical profile having a major diameter and a minor diameter; and the drive mechanism further comprises at least one tensioner pulley substantially coplanar with the drive pulley and the flywheel and positioned so as to engage the drive belt.
 7. The apparatus of claim 6, wherein: a first quadrant is defined as an arcuate segment of the flywheel between the major diameter and the minor diameter; and the crankpin is mounted on the flywheel within the first quadrant.
 8. The apparatus of claim 7, wherein: a radially-outwardly projecting fastening plate is formed on the flywheel laterally offset from the drive belt; and the crankpin is mounted on the fastening plate.
 9. The apparatus of claim 7, wherein: the flywheel further comprises: a hub rotatably installed on a flywheel shaft mounted to the frame substantially perpendicular to the flywheel; two or more radial spokes connecting the hub to the outer rim, two of the spokes being substantially aligned with the major diameter; and two or more masses symmetrically located within the outer rim substantially along the major diameter; and the crankpin is mounted on a spoke.
 10. The apparatus of claim 2, wherein: the crankpin is formed with a free end extending beyond the intake block; and a roller bearing is installed on the free end so as to ride within the slot.
 11. The apparatus of claim 2, wherein the cavity is in communication with the lower chamber and the upper chamber; the piston assembly further comprises an upper piston valve installed adjacent to the piston body so as to selectively seal the upper chamber from the cavity; and the air line is installed in the cylinder so as to communicate with both the upper chamber and the lower chamber, whereby upward travel of the piston body as caused by the drive mechanism acting through the piston rod closes the upper piston valve so as to compress the air within the upper chamber, and whereby downward travel of the piston body as caused by the drive mechanism acting through the piston rod opens the upper piston valve and allows ambient air to be drawn through the piston rod bore, the at least one opening, and the cavity into the upper chamber.
 12. The apparatus of claim 11, wherein: an upper one-way valve is installed in the cylinder in communication with the upper chamber; a lower one-way valve is installed in the cylinder in communication with the lower chamber; and the air lines are connected to the upper and lower one-way valves, whereby the air compressed in the lower chamber when the piston body travels downward is forced through the lower one-way valve and into the air line leading to the tank, and whereby the air compressed in the upper chamber when the piston body travels upward is forced through the upper one-way valve and into the air line leading to the tank.
 13. The apparatus of claim 11, wherein: the cylinder has an upper end formed by an upper cylinder wall and a lower end formed by a lower cylinder wall; an upper chamber plate is sealably installed within the cylinder offset from the upper cylinder wall so as to form therebetween an upper breathing chamber, the upper chamber plate being formed with at least one selectively sealable upper breathing hole communicating between the upper chamber and the upper breathing chamber; the upper cylinder wall and the upper chamber plate are formed with substantially axially aligned piston bores for the passage therethrough of the piston rod; a lower chamber plate is sealably installed within the cylinder offset from the lower cylinder wall so as to form therebetween a lower breathing chamber, the lower chamber plate being formed with at least one selectively sealable lower breathing hole communicating between the lower chamber and the lower breathing chamber; and the air lines are connected to the cylinder so as to communicate with the upper and lower breathing chambers, whereby the air compressed in the lower chamber when the piston body travels downward is selectively forced through the at least one lower breathing hole, into the lower breathing chamber, and then into the air line leading to the tank, and whereby the air compressed in the upper chamber when the piston body travels upward is selectively forced through the at least one upper breathing hole, into the upper breathing chamber, and then into the air line leading to the tank.
 14. The apparatus of claim 1, wherein: the cylinder is rigidly installed on the frame; and the drive mechanism comprises: a chain drive mounted to the frame and having a driving sprocket and an idler sprocket in spaced apart relationship, the centers of the sprockets being along a centerline parallel to and offset from the axis of the cylinder, the chain drive further having a chain configured to engage the sprockets, whereby a drive shaft of the motor turns the driving sprocket so as to drive the chain about the sprockets; a guide rod mounted between offset attachment blocks installed on the frame, the guide rod being parallel to and offset from the centerline of the sprockets opposite the cylinder, the guide rod having a sliding bushing slidably operable thereon between the respective attachment blocks; a track arm rigidly mounted to the sliding bushing at an angle between zero and ninety degrees relative to the guide rod, the track arm having a slot formed therein; an intake block rigidly mounted on the track arm so as to connect the piston rod to the track arm, the intake block being formed with at least one passage for the communication of ambient air through the passage and into the hollow bore; and a cam follower mounted on the chain so as to project into and engage the slot, whereby movement of the chain about the sprockets translates into oscillating linear movement of the track arm and simultaneous axial displacement of the piston body within the cylinder as acted on by the piston rod rigidly mounted to the track arm through the intake block.
 15. The apparatus of claim 1, wherein: a first cylinder and a second cylinder are rigidly installed on the frame in a substantially aligned offset arrangement, the first cylinder formed with a first lower cylinder wall and having a first piston body sealingly and slidably installed therein so as to form a first upper chamber above the first piston body and a first lower chamber below the first piston body, the first piston body being further formed with a first cavity in communication with the first lower chamber, the second cylinder formed with a second lower cylinder wall and having a second piston body sealingly and slidably installed therein so as to form a second upper chamber above the second piston body and a second lower chamber below the second piston body, the second piston body being further formed with a second cavity in communication with the second lower chamber; a first piston rod and a second piston rod are rigidly connected at respective adjacent ends to the drive mechanism, the first piston rod having a first hollow bore and at least one first breathing hole communicating between the first hollow bore and the ambient air, the first piston rod passing through the first cylinder and the first upper chamber so as to be connected at a first piston end opposite the drive mechanism to the first piston body, the first piston rod having at least one first opening formed therein such that the first hollow bore is in communication with the first cavity, the second piston rod having a second hollow bore and at least one second breathing hole communicating between the second hollow bore and the ambient air, the second piston rod passing through the second cylinder and the second upper chamber so as to be connected at a second piston end opposite the drive mechanism to the second piston body, the second piston rod having at least one second opening formed therein such that the second bore is in communication with the second cavity; at least one first escape passage is formed within the first cylinder so as to selectively communicate between the first upper chamber and the first lower chamber, the first escape passage having a first longitudinal length greater than the thickness of the first piston body; at least one second escape passage is formed within the second cylinder so as to selectively communicate between the second upper chamber and the second lower chamber, the second escape passage having a second longitudinal length greater than the thickness of the second piston body; a first lower piston valve is installed on the first piston body so as to selectively seal the first lower chamber from the first cavity; a second lower piston valve is installed on the second piston body so as to selectively seal the second lower chamber from the second cavity; a first one-way valve is installed in the first cylinder in fluid communication with the first upper chamber; a second one-way valve is installed in the second cylinder in fluid communication with the second upper chamber; and the air lines are connected to the first and second one-way valves, whereby movement of the drive mechanism in a first direction acts on the first piston rod to cause the first piston body to travel toward the first lower chamber, closing the first lower piston valve and compressing the air in the first lower chamber until the first piston body nears the first lower cylinder wall such that the at least one first escape passage is temporarily no longer sealed by the first piston body so as to allow the compressed air to pass from the first lower chamber through the at least one first escape passage and into the first upper chamber, and whereby movement of the drive mechanism in the first direction simultaneously acts on the second piston rod to cause the second piston body to travel toward the second upper chamber, further compressing the air in the second upper chamber and opening the second lower piston valve to allow ambient air to be drawn through the at least one second breathing hole, the second hollow bore, the at least one second opening, and the second cavity into the second lower chamber, and whereby movement of the drive mechanism in an opposite second direction acts on the first piston rod to cause the first piston body to travel toward the first upper chamber, further compressing the air in the first upper chamber and opening the first lower piston valve to allow ambient air to be drawn through the at least one first breathing hole, the first hollow bore, the at least one first opening, and the first cavity into the first lower chamber, and whereby movement of the drive mechanism in the second direction simultaneously acts on the second piston rod to cause the second piston body to travel toward the second lower chamber, closing the second lower piston valve and compressing the air in the second lower chamber until the second piston body nears the second lower cylinder wall such that the at least one second escape passage is temporarily no longer sealed by the second piston body so as to allow the compressed air to pass from the second lower chamber through the at least one second escape passage and into the second upper chamber.
 16. The apparatus of claim 15, wherein the drive mechanism comprises: a piston rod mounting block mounted to the respective adjacent ends of the first and second piston rods so as to rigidly support the first and second piston rods in a substantially coaxial arrangement, the first and second breathing holes being positioned along the respective first and second piston rods so as to be clear of the piston rod mounting block; a yoke block rigidly mounted to the piston rod mounting block, the yoke block having an outwardly-opening yoke channel formed therein at an angle between zero and ninety degrees relative to the piston rod mounting block; a cam pulley mounted to the frame so as to rotate about a cam pulley shaft, the cam pulley having a cam follower projecting therefrom offset from the cam pulley shaft and oriented so as to extend into and engage the yoke channel; a drive pulley installed on a drive shaft of the motor so as to be substantially coplanar with the cam pulley; and a drive belt engaging the drive pulley and the cam pulley so that torque from the motor is transmitted to the cam pulley though the drive belt, whereby rotational movement of the cam pulley translates into oscillating linear movement of the piston rod mounting block and simultaneous axial displacement of the first and second piston bodies within the respective first and second cylinders as acted on by the respective first and second piston rods rigidly mounted within the piston rod mounting block.
 17. The apparatus of claim 1, wherein: the cavity is in communication with the lower chamber and the upper chamber; the piston assembly further comprises an upper piston valve installed adjacent to the piston body so as to selectively seal the upper chamber from the cavity; and the air line is installed in the cylinder so as to communicate with both the upper chamber and the lower chamber, whereby upward travel of the piston body as caused by the drive mechanism acting through the piston rod closes the upper piston valve so as to compress the air within the upper chamber, and whereby downward travel of the piston body as caused by the drive mechanism acting through the piston rod opens the upper piston valve and allows ambient air to be drawn through the hollow bore, the at least one opening, and the cavity into the upper chamber.
 18. The apparatus of claim 17, wherein: the piston body comprises an upper piston wall and an offset lower piston wall; the cavity comprises an upper piston bore formed in the upper piston wall in communication with a lower piston bore formed in the lower piston wall, the lower piston bore having an internal diameter substantially equivalent to the external diameter of the piston rod, the piston rod being seated within the lower piston bore so as to communicate therewith through the hollow bore, the upper piston bore having an internal diameter greater than the external diameter of the piston rod, the piston rod being formed with one or more cross-holes positioned therein so as to communicate between the hollow bore and the upper piston bore; an outwardly-opening annular channel is formed in the lower piston wall; a lower o-ring is seated within the annular channel; the lower piston valve comprises a lower valve disk movably mounted on the piston body substantially adjacent to the lower piston wall so as to selectively contact the o-ring and seal the lower piston bore; the upper piston bore is further formed with an outwardly-opening countersink; the upper piston valve comprises a collar slidably installed on the piston rod, the collar having a lower end substantially adjacent to the upper piston wall and formed with a shoulder; and an upper o-ring is seated against the shoulder so as to selectively contact the countersink and seal the upper piston bore.
 19. The apparatus of claim 17, wherein: the cylinder has an upper end having a downwardly-facing upper surface intersected by an upper exit bore and a lower end having an upwardly-facing lower surface intersected by a lower exit bore, the upper exit bore being configured to selectively receive the upper piston valve and the lower exit bore being configured to selectively receive the lower piston valve; an upper release valve is installed within the piston body offset from the cavity so as to selectively communicate between the upper chamber and the lower chamber, the upper release valve having an upwardly-projecting, spring-biased upper contact pin configured to contact the upper surface after the piston body has traveled upwardly sufficiently to receive the upper piston valve within the upper exit bore, whereby displacement of the upper contact pin temporarily opens the upper release valve and allows compressed air to pass from the upper chamber through the upper release valve and into the lower chamber; and a lower release valve is installed within the piston body offset from the cavity and from the upper release valve so as to selectively communicate between the lower chamber and the upper chamber, the lower release valve having a downwardly-projecting, spring-biased lower contact pin configured to contact the lower surface after the piston body has traveled downwardly sufficiently to receive the lower piston valve within the lower exit bore, whereby displacement of the lower contact pin temporarily opens the lower release valve and allows compressed air to pass from the lower chamber through the lower release valve and into the upper chamber.
 20. The apparatus of claim 17, wherein: the piston body comprises an upper piston wall and an offset lower piston wall; the cavity comprises an annular space substantially between the upper piston wall and the lower piston wall, one or more upper breathing holes formed in the upper piston wall so as to selectively communicate between the upper chamber and the annular space, and one or more lower breathing holes formed in the lower piston wall so as to selectively communicate between the lower chamber and the annular space, the piston rod being formed with one or more cross-holes positioned therein so as to communicate between the hollow bore and the annular space; an outwardly-opening lower annular channel is formed in the lower piston wall about each lower breathing hole; a lower o-ring is seated within each lower annular channel; the lower piston valve comprises a lower valve disk movably mounted on the piston body substantially adjacent to the lower piston wall so as to selectively contact each lower o-ring and seal the lower breathing holes; an outwardly-opening upper annular channel is formed in the upper piston wall about each upper breathing hole; an upper o-ring is seated within each upper annular channel; and the upper piston valve comprises an upper valve disk movably mounted on the piston body substantially adjacent to the upper piston wall so as to selectively contact each upper o-ring and seal the upper breathing holes.
 21. The apparatus of claim 17, wherein: the piston body comprises an upper piston wall and an offset lower piston wall; the cavity comprises an annular space substantially between the upper piston wall and the lower piston wall, one or more upper breathing holes formed in the upper piston wall so as to selectively communicate between the upper chamber and the annular space, and one or more lower breathing holes formed in the lower piston wall so as to selectively communicate between the lower chamber and the annular space, the piston rod being formed with one or more cross-holes positioned therein so as to communicate between the hollow bore and the annular space; the lower piston valve comprises a lower valve disk movably mounted on the piston body substantially adjacent to the lower piston wall, the lower valve disk being formed with concentric upwardly-opening first and second annular channels, the channels being configured to define a seal area therebetween that is substantially adjacent to the lower breathing holes; a first lower o-ring is seated within the first annular channel and a second lower o-ring is seated within the second annular channel, the o-rings selectively contacting the lower piston wall so as to seal the lower breathing holes; an outwardly-opening upper annular channel is formed in the upper piston wall about each upper breathing hole; an upper o-ring is seated within each upper annular channel; and the lower piston valve comprises an upper valve disk movably mounted on the piston body substantially adjacent to the upper piston wall so as to selectively contact each upper o-ring and seal the upper breathing holes.
 22. The apparatus of claim 21, wherein: a plug is installed within the hollow bore substantially at the piston end, the plug being formed with an outwardly-opening threaded hole; the lower valve disk is further formed with a clearance hole offset from and substantially concentric with the first and second annular channels; a fastening screw having a head and a threaded body projecting therefrom is passed through the clearance hole and threadably installed within the threaded hole; and a return spring is positioned about the threaded body between the head and the lower valve disk so as to bias the lower valve disk upwardly.
 23. The apparatus of claim 1, wherein: the cylinder comprises an annular cylinder wall having an inside surface; the piston body comprises an upper piston wall, an offset lower piston wall, and an annular piston wall formed between the upper piston wall and the lower piston wall so as to define at least one radially-outwardly-opening circumferential piston ring channel; a piston ring is inserted within the piston ring channel so as to sealably and slidably contact the inside surface.
 24. The apparatus of claim 23, wherein the piston ring is formed with a diagonal slit therethrough.
 25. The apparatus of claim 23, wherein the piston ring is formed with one or more radially-outwardly-opening circumferential piston ring grooves.
 26. The apparatus of claim 23, wherein: the annular piston wall is formed with a radially-outwardly-projecting circumferential rib so as to define an upper piston ring channel between the rib and the upper piston wall and a lower piston ring channel between the rib and the lower piston wall; an upper piston ring is inserted within the upper piston ring channel and a lower piston ring is inserted within the lower piston ring channel so as to cooperate to sealably and slidably contact the inside surface.
 27. The apparatus of claim 23, wherein: the annular piston wall is formed with a radially-outwardly opening circumferential piston groove; and a piston o-ring is seated within the piston groove such that the piston ring inserted within the piston ring channel is radially-outwardly of the piston o-ring, whereby the piston ring is effectively sealed between the inside surface and the piston o-ring.
 28. The apparatus of claim 23, wherein the annular piston wall is formed with multiple radially-inwardly-projecting longitudinal fins.
 29. The apparatus of claim 1, wherein: the cylinder has an upper end formed by an upper cylinder wall and a lower end formed by a lower cylinder wall; an upper chamber plate is sealably installed within the cylinder offset from the upper cylinder wall so as to form therebetween an upper breathing chamber, the upper chamber plate being formed with at least one selectively sealable upper breathing hole communicating between the upper chamber and the upper breathing chamber; the upper cylinder wall and the upper chamber plate are formed with substantially axially aligned piston bores for the passage therethrough of the piston rod; a lower chamber plate is sealably installed within the cylinder offset from the lower cylinder wall so as to form therebetween a lower breathing chamber, the lower chamber plate being formed with at least one selectively sealable lower breathing hole communicating between the lower chamber and the lower breathing chamber; and the air lines are connected to the cylinder so as to communicate with the upper and lower breathing chambers, whereby the air compressed in the lower chamber when the piston body travels downward is selectively forced through the at least one lower breathing hole, into the lower breathing chamber, and then into the air line leading to the tank, and whereby the air compressed in the upper chamber when the piston body travels upward is selectively forced through the at least one upper breathing hole, into the upper breathing chamber, and then into the air line leading to the tank.
 30. The apparatus of claim 29, wherein: an upwardly-opening upper annular channel is formed in the upper chamber plate about each upper breathing hole; an upper o-ring is seated within each upper annular channel; and an upper chamber disk is movably mounted within the upper breathing chamber substantially adjacent to the upper chamber plate so as to selectively contact the upper o-rings and seal the upper breathing holes.
 31. The apparatus of claim 29, wherein: an upwardly-opening counterbore is formed substantially concentric with each upper breathing hole; an upwardly-opening upper annular channel is formed in the upper chamber plate substantially about the piston bores and connecting the upper breathing holes; an upper o-ring is seated within each counterbore; and a ball is movably inserted within each counterbore so as to selectively contact each upper o-ring and seal the upper breathing holes.
 32. The apparatus of claim 29, wherein: a lower chamber disk is movably mounted within the lower breathing chamber substantially adjacent to the lower chamber plate, the lower chamber disk being formed with an upwardly-opening lower annular channel and being further formed with at least one lower chamber passage radially-outwardly offset from the lower annular channel; a lower o-ring is seated within the lower annular channel so as to selectively contact the lower chamber plate and seal the at least one lower breathing hole; and a return spring is positioned substantially between the lower chamber disk and the lower cylinder wall so as to bias the lower chamber disk upwardly.
 33. The apparatus of claim 29, wherein: an upwardly-projecting support post is formed on the lower cylinder wall so as to extend into the lower breathing chamber; a upwardly-opening counterbore is formed in the lower chamber plate substantially concentric with the at least one lower breathing hole; a ball is movably inserted within the counterbore so as to selectively seal the at least one lower breathing hole; and a return spring is positioned about the support post between the ball and the lower cylinder wall so as to bias the ball upwardly.
 34. The apparatus of claim 1, wherein: a first pillow block bearing is installed on the tank, the first pillow block bearing having a first through hole; a second pillow block bearing is installed on the tank offset from the first pillow block bearing, the second pillow block bearing having a second through hole substantially coaxial with the first through hole; the drive mechanism comprises: a flywheel shaft rotatably installed within the first and second through holes of the first and second pillow block bearings, the flywheel shaft having a flywheel end and an opposite drive arm end; a flywheel rigidly mounted to the flywheel shaft substantially at the flywheel end, the flywheel having a flywheel crankpin installed thereon; a drive arm rigidly mounted to the flywheel shaft substantially at the drive arm end, the drive arm having a drive arm crankpin installed thereon, the drive arm being mounted on the flywheel shaft such that the drive arm crankpin is out of phase with the flywheel crankpin; a drive pulley installed on a drive shaft of the motor so as to be substantially coplanar with the flywheel; a drive belt engaging the drive pulley and the flywheel so that rotation of the drive shaft is transmitted to the flywheel through the drive belt, whereby rotation of the flywheel is transmitted to rotation of the drive arm through the flywheel shaft; a flywheel intake block pivotally mounted on the flywheel crankpin; and a drive arm intake block pivotally mounted on the drive arm crankpin; a first cylinder and a second cylinder are pivotally installed on the frame in a substantially offset arrangement, the first cylinder having a first piston body sealingly and slidably installed therein so as to form a first upper chamber above the first piston body and a first lower chamber below the first piston body, the first piston body being further formed with a first cavity in communication with the first lower chamber, the second cylinder having a second piston body sealingly and slidably installed therein so as to form a second upper chamber above the second piston body and a second lower chamber below the second piston body, the second piston body being further formed with a second cavity in communication with the second lower chamber; a first piston rod being rigidly connected at a first drive end to the flywheel intake block and a second piston rod being rigidly connected at a second drive end to the drive arm intake block, the first piston rod having a first hollow bore configured to communicate with the ambient air through the flywheel intake block, the first piston rod passing though the first cylinder and the first upper chamber so as to be connected at a first piston end opposite the first drive end to the first piston body, the first piston rod having at least one first opening formed therein such that the first hollow bore is in communication with the first cavity, the second piston rod having a second hollow bore configured to communicate with the ambient air through the drive arm intake block, the second piston rod passing through the second cylinder and the second upper chamber so as to be connected at a second piston end opposite the second drive end to the second piston body, the second piston rod having at least one second opening formed therein such that the second bore is in communication with the second cavity; a first lower piston valve is installed on the first piston body so as to selectively seal the first lower chamber from the first cavity and a second lower piston valve is installed on the second piston body so as to selectively seal the second lower chamber from the second cavity; and the air lines are connected to the first and second cylinders so as to communicate with the first and second lower chambers, whereby rotation of the flywheel acts on the first piston rod through the flywheel crankpin and the flywheel intake block to cause the first piston body to travel within the first cylinder, alternately opening the first lower piston valve to pull ambient air through the first hollow bore and the first cavity into the first lower chamber and closing the first lower piston valve to compress the air in the first lower chamber, and whereby rotation of the flywheel simultaneously acts on the second piston rod through the flywheel shaft, the drive arm, the drive arm crankpin and the drive arm intake block to cause the second piston body to travel within the second cylinder, alternately opening the second lower piston valve to pull ambient air through the second hollow bore and the second cavity into the second lower chamber and closing the second lower piston valve to compress the air in the second lower chamber, the opening of the first lower piston valve being non-concurrent with the opening of the second lower piston valve and the closing of the first lower piston valve being non-concurrent with the closing of the second lower piston valve due to the flywheel crankpin and the drive arm crankpin being out of phase.
 35. The apparatus of claim 1, wherein the piston assembly further comprises an acoustical sleeve installed within the hollow bore.
 36. An air compression apparatus having a frame and a tank mounted to the frame, the improvement comprising: at least one piston assembly configured to move within a respective cylinder mounted to the frame, the piston assembly comprising: a piston body sealingly and slidably installed within the cylinder; a piston rod having a hollow bore communicating between a drive end and a piston end, the piston rod being connected to the piston body substantially at the piston end; and a means for selectively sealing the hollow bore substantially at the piston end; a means for driving the piston assembly within the cylinder such that the hollow bore is in communication with ambient air substantially at the drive end; and at least one air line connected between the cylinder and the tank, whereby upward travel of the piston body as caused by the driving means acting through the piston rod opens the sealing means and allows ambient air to be drawn through the hollow bore into the lower chamber, and whereby downward travel of the piston body as caused by the driving means acting through the piston rod closes the sealing means so as to compress the air within the lower chamber and pass the compressed air through the air line to the tank.
 37. An air compression apparatus, comprising: a cylinder having a gland, an opposite end wall, and an annular wall therebetween defining an inside surface and a central axis; a piston body inserted within the cylinder in sliding engagement with the inside surface so as to define a first chamber between the piston body and the end wall and a second chamber between the piston body and the gland, the piston body being further formed with a cavity in communication with at least the first chamber; a piston rod passing though the gland and connected to the piston body, the piston rod having a hollow bore therein configured to communicate with ambient air outside the cylinder and configured to communicate with the cavity of the piston body inside the cylinder; a first inertial valve cooperating with the piston body to selectively seal the first chamber from the cavity; and a first exit valve installed in the cylinder so as to communicate with the first chamber, whereby movement of the piston body toward the gland opens the first inertial valve and allows ambient air to be drawn through the hollow bore and the cavity into the first chamber, and whereby movement of the piston body toward the end wall closes the first inertial valve so as to compress the air within the first chamber and pass the compressed air through the first exit valve.
 38. The apparatus of claim 37, wherein: the cavity is in further communication with the second chamber; a second inertial valve cooperates with the piston body to selectively seal the second chamber from the cavity; and a second exit valve is installed in the cylinder so as to communicate with the second chamber, whereby movement of the piston body toward the end wall opens the second inertial valve and allows ambient air to be drawn through the hollow bore and the cavity into the second chamber, and whereby movement of the piston body toward the gland closes the second inertial valve so as to compress the air within the second chamber and pass the compressed air through the second exit valve.
 39. The apparatus of claim 38, further comprising a means for driving the piston rod such that substantially all forces act on the piston body substantially along the central axis.
 40. An air compression apparatus having a frame and a tank and a motor mounted to the frame, comprising: at least one piston assembly operably configured to move within a respective cylinder pivotally mounted to the frame, the piston assembly comprising: a piston body sealingly and slidably installed within the cylinder; a piston rod passing through the cylinder so as to be connected to the piston body; and at least one air inlet and at least one air outlet formed in the cylinder; a drive mechanism operably connected to the motor and to the piston assembly, the drive mechanism comprising: an elliptical flywheel rotatably mounted to the frame; a drive pulley installed on a drive shaft of the motor so as to be substantially coplanar with the flywheel; a drive belt engaging the drive pulley and the flywheel so that torque from the motor is transmitted to the flywheel through the drive belt; and a crankpin mounted on the flywheel and rotatably connected to the piston rod, whereby rotational movement of the flywheel translates into oscillating movement of the cylinder and simultaneous axial displacement of the piston body within the cylinder; and at least one air line connected between the cylinder and the tank for the passage of compressed air therethrough, whereby travel in a first direction of the piston body as caused by the drive mechanism acting through the piston rod draws ambient air through the air inlet into the cylinder, and whereby travel in a second direction of the piston body as caused by the drive mechanism acting through the piston rod compresses the air within the cylinder.
 41. A method of compressing air, comprising the steps of: connecting a hollow piston rod to a piston body operating within a cylinder; introducing ambient air into the cylinder through the hollow piston rod; and moving the piston body within the cylinder to compress the air.
 42. The method of claim 41, comprising the further steps of: opening a lower piston valve to allow ambient air to be drawn through the hollow piston rod into a lower chamber of the cylinder; and alternately closing the lower piston valve so as to compress the air within the lower chamber.
 43. The method of claim 41, comprising the further steps of: opening a lower piston valve to allow ambient air to be drawn through the hollow piston rod into a lower chamber of the cylinder while closing an upper piston valve to compress the air within an upper chamber of the cylinder; and alternately closing the lower piston valve so as to compress the air within the lower chamber while opening the upper piston valve to allow ambient air to be drawn through the hollow piston rod into the upper chamber.
 44. The method of claim 41, comprising the further step of oscillating the cylinder.
 45. The method of claim 44, wherein the step of oscillating the cylinder comprises the further steps of: shifting the upper end of the cylinder arcuately about a pivot pin on which the base of the cylinder is mounted; and shifting the lower end of the cylinder arcuately about the pivot pin and arcuately about a pivot shaft offset from the pivot pin along a pivot arm.
 46. A compression apparatus comprising: a piston body operating within a cylinder; a piston rod formed with a hollow bore and connected to the piston body such that the hollow bore is in selective communication with the cylinder; and a drive mechanism coupled to the piston rod through an intake block, whereby ambient air is selectively introduced into the cylinder through the intake block and the hollow bore for compression by the piston body as the piston body travels within the cylinder as caused by the drive mechanism acting through the piston rod. 